CA1107452A - Respirator - Google Patents
RespiratorInfo
- Publication number
- CA1107452A CA1107452A CA289,674A CA289674A CA1107452A CA 1107452 A CA1107452 A CA 1107452A CA 289674 A CA289674 A CA 289674A CA 1107452 A CA1107452 A CA 1107452A
- Authority
- CA
- Canada
- Prior art keywords
- indicator
- respirator
- cartridge
- disposable
- vinyl chloride
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62B—DEVICES, APPARATUS OR METHODS FOR LIFE-SAVING
- A62B18/00—Breathing masks or helmets, e.g. affording protection against chemical agents or for use at high altitudes or incorporating a pump or compressor for reducing the inhalation effort
- A62B18/08—Component parts for gas-masks or gas-helmets, e.g. windows, straps, speech transmitters, signal-devices
- A62B18/088—Devices for indicating filter saturation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T436/00—Chemistry: analytical and immunological testing
- Y10T436/19—Halogen containing
- Y10T436/196666—Carbon containing compound [e.g., vinylchloride, etc.]
Abstract
A B S T R A C T
A disposable valveless chemical cartridge respirator for filtration of vinyl chloride monomer having an end of service life indicator is disclosed.
A disposable valveless chemical cartridge respirator for filtration of vinyl chloride monomer having an end of service life indicator is disclosed.
Description
r~ ~ F.N. 913,250 ~ 110745Z
RESPIRATOR
The present invent~on relates to valveless chemlcal cartrldge resplrators for filtratlon of vinyl chlor~de monomer (VCM) and hav~ng an end of service life indlcator as an integral par~ thereofO So far as ~s known, all commercially avallable ~.
chem~cal cartrldge resplrators are equipped with inhalation and exhalat~on valvesO Inhalation valves prevent exhaled alr from entertng the oartridge and contam~nating the filter media w7th excess humid~tyO Exhalat~on valves permit easier exhalatlon slnce the res~stance to flow of air therethrough ~s very lowO
The prlor art, ~ncluding various governmental agencies, has treated as lnv~olable fact that respirators for toxic vapors and gases must be equipped with lnhalatlon and exhalation valves to be ef~ect1veO Thus, reference to Subpart L of Part ll of ~ S~bchapter B of Chapter l, Title 30, Code of Federal Regula-: t10ns, Federal Reg~ster, VolO 37, NoO 59, March 25, 1972, and Subpart N, Federal Reg1ster, Yol. 39, No. 251, December 30, 1974, (hereafter to be referred to as 30 CFR Part ll, Subpart and Sectlon) wlll conf~rm the fact that approval of chem~cal cartr~dge resp~rators ~s predicated on structures : contaln~ng inhalat~on and exhalation valvesO The Austral~an Standards CZll and Zl8-1968 for "Resplratory Protectlve Dev~ces" and Brlt~sh Standard BS 2091:1969 for "Respirators : for Protect~on Against Harmful Dusts and Gases" are slm11arly prem~sed.
; The present 1nvent~on relates to long-llfe valveless chemical cartrldge resplrators ~or vinyl chloride monomer and 1s intended for uses where approval by the Minlng Enforcement and Sa~ety Administratlon or the National Institute of Occu-pational Saf`ety and Health ~NIOSH) would be requiredO
It was early recogn7zed that any respirator for vinyl chlorlde ~onomer would requlre approval ~rom the pertlnent regulatory agency in order to be a vidble commerclal ''~
~
``` ~1~17~Z
productO The requirements for NIOSH approval of a vinyl chlorlde resplrator are found in 30 CFR Part 11, Subpart N, Sections 11-200 through 11-2080 Under these regulations, a vlnyl chlorlde respirator must last at least 120 m7nutes before 7 ppm VCM penetrates the cartr~dgeO Accordingly, although cons~derable effort was expended ~n attempts to meet the appllcable standards for cartrldge type respirators by us7ng a wide variety of commercially ava~lable carbons in a test cartridge with d~mensions approximating a chemical cartridge for a resp~rator, no carbon was found which lasted more than 70 minutes when tested under the condit~ons prescribed ln Subpart N~ Sectlon 11-203. Other efforts were directed to different media formulatlons and cartridge configuratl3nsO
It was then d1scovered that by the seemingly s~mple exped~ent of el~m~natlng the ~nhalation and exhalation valves o~ the known prlor art chemical cartridge resplrators, low pressure-drop valveless f~lter-type respirators hav~ng break-through t~mes to toxic vapors and gases at least double the breakthrough t~mes of conventlonal valved resp~rators utillzlng identlcal chemical cartridges were obtained. Addltlonally, it was found that, dependlng on the type of carbon utlllzed, the amount of ~ilter media in the resplrator could be reduced lo about 50% or less of the p~ev~ously "required" amount thus maklng ~t posslble to greatly reduce the slze and weight of the chemlcal cartr~dge, resulting in a lighter and more comfortab7e respirator~
There st111 remained the necesslty of providlng an end of service l~fe 7nd~cator 7n order for the respirator to ~ualify for approval under the above noted governmenta7 standardsO An extremely rellable yet exceed1ngly s~mple end of servlce llfe indlcator which undergoes a dramatic and d~st~nct colo~ change has now been d~scoveredO
~1~74S2 According to:the present invention, there is provided a disposable valveless chemical cartridge respirator for filtration of vinyl chloride monomer comprising a body including a facepiece having means for peripherally sealing contact with at least that portion of a human head which includes the nose and mouth, associated fastening means for holding said respirator in position on the head, a cartridge on said body having an air entrance and an air exit communicating with the interior of said respirator and contain-ing therewithin filter media comprising activated carbon and an end of service life indicator, said cartridge having a volume of about 220 cc. for said indicator and said filter media, said indicator being disposed across the path of air intake at the entrance of said cartridge, said filter media and indicator being adapted for adsorption thereon of a vinyl chloride monomer contaminant upon inhalation therethrough, said indicator including means upon exposure to a predetermined amount of vinyl chloride monomer undergoing a dramatic and distinct color change to indicate the end of service life o said respirator.
-2a-i74~;2 In the accompanying drawing which illustrates the nvention:
Flgure l ls a front eleYational view of a chemical cartridge resp~rator embodylng the principles of the present tnventlon, and -F1gure 2 is an enlarged view ,partly in section,of the respirator of F~gure l.
Referring more particularly to Figure 1 of the drawlng, lO denotes a valveless cartridge respirator comprising a transparen~ molded plastic body ll of a generally pear-shaped contour and having an inwardly turned marginal lip or edge portion to provide an air-tight seal. Chemical cartridge 20 is formed as an integral part of body ll and comprises a shallow, generally cylindroid molded transparent plastic container 21 prov~ded with openings 12 to form a mesh for air passage~ Cartri~ge 20 has a volume of about 220 cc. for the indicator and fflter media ~sorbent). Starting from the front or left as viewed in F~gure 2, the cartridge 20 contalns a nonwoven retainer web 22, 30 cc. of indicator 23, l90 ccO of activated carbon 24 and a second nonwoven retainer web 250 A molded mesh plate 26 is welded to the back of cartridge 20 to hold the contents tightly in placeO A molded, polymeric facepiece 27 and sultable headbands 13 are laid in place inside a crimping llp 28 forming the per7phery at body ll.
The lip ls heated, crlmped, and upon cooling tlghtly holds the facepiece 27 and bands 13 in placeO The respirator lO
may, if deslred, be equipped wtth a speaking diaphragm ~not shown)c The lnd1cator of the present inventlon comprises spec~ally prepared activated alumina granules coated flrst from a 1% so7ution of KMnO4, which is then reduced to what ts belie~ed to be MnO2, and then coated from a 0O55~ solution of potassium permanganate. The indicator is viewed through the side wall of the cartridge all along the edge nearest the entrance to the cartridgeO The init~al color is a light purple or purple-pink, hereina~ter referred to as purple for simplicity. Upon exposure to vinyl chloride, the potassium permanganate is reduced to manganese dioxide such that there is a slow, continuous color change from the purple to a light brown or tan-beige (hereafter referred to as brown), the color of manganese dioxide.
The indicator of the present invention is prepared by first coating alumina granules with potassium permanganate whlch is then reduced to the brown manganese dioxide which acts as a partial screen and color enhancer for` the final coating of potassium permanganate. The brown MnO2 coating on the granules acts as a color screen to hide some of the purple of the KMnO4.
The more brown MnO2 present, the more purple KMnO4 is covered upO
Thus, for any given indicator life (modified NIOSH VCM test conditions), say 260 minutes, one must adjust the KMnO4 coating concentration for a given MnO2 coating concentration so that the indicator is visually brown at the end of the period. For any MnO2 concentration (greater than zero), there will be some resi-dual purple KMnO4 left on the indicator granule at the end of the indicator life but it will be visuall~ screened out by the brown MnO2. Thls is illustrated by the fact that an indicator sample coated from a 1% manganese d1oxide solution and a 0.55%
potassium permanganate solution results in an indicator life of 256 minutes, about the same life as the indicator coated from 0%
manganese dioxide and a 001% KMnO4 solution. The 0% MnO2 - 0.1%
KMnO4 lndlcator ~s very llght pink in color and changes only s11ghtly to a l1ght cream color when spent. On the other hand, the 1% MnO2 - 0055% KMnO4 ind7cator changes quite dramatically from the starting purple to the endpoint brown colorO The color contrast from start to f~nish for the latter is much greater and 7~52 the~eby makes the indlcator much easier for the user to read.
The ~ollow~ng table shows several lndlcator samples:
%KMnO4 on MnO2 solutlon KMnO4 solutlon granule Indicator conoentrat70n concentrat~on (by wel~ht) llfe (m~nutes) 0% 0O1% 0.036 257 1.0% 0O35% 0.134 220 lu0% 0~55% 0.228 256 1O0% 0O70% 0.352 330 lo25% 0.55% 0.231 180 1025% 0.80% 0.476 333 The 7nd;cator ~s made by preparing a solut1on of known concentratlon of potass~um permanganate in waterO Activated alum~na granules in a s~ze range of 8 to 14 mesh, avallable from Reynolds Chem~cal Products, is immersed in the solution untll the solutlon has absorbed onto the alumina granules to its equilibrlum level. Excess solut1On is drained off and the granules are dried at about 230F. (105C.) under vacuum with rotation. The coated granules are heated to about 500F. (288~C.) at atmospheric pressure for a period of time necessary to reduce the potassium permanganate to manganese~d1oxlde. A second solution of known concentration of potassium permanganate ln water is prepared. The manganese dlox1de coated alumina granules are immersed in the solution untll the absorptlon reaches an equilibrium levelO The excess solutlon is drained off and the granules are again dried at about 230~F~ (105C.~ under vacuum wlth rotationO
As noted hereinabove, prlor workers in the chemical cartridge type resplrator art have considered inhalation and exhalatlon valves to be essential for proper respirator func-tionlng~ Inhalatlon valves were thought to be necessary to avold contaminating the filter medla with excess1ve humldity, siJnce ~t was "known" that the adsorption cdpacity of the fllter med~a was detrlmentall~ af~ected by h~gh humld~ty, especlally ~elatlve hum~d~t~es abo~e 50%O Exhalatlon valves were, of 17~S2 course, necessary to enable respiration to take p1ace since one could not exhale through the f~lter medla with the inhalation valve ln place. In add~t~on, the exhalatlon valves were deslgned such tha~ the reslstance to flow of air therethrough was very low~
It has now been discovered that any deleterious effect on the fllter med~a caused by the high humidity of exhaled a1r is more than offset by the apparent desorption of the contamlnant from the ~lter media, such that the breakthrough tlme of the filter med~a in a valveless respirator is at least doubled over a conventional valved respirator. Because of this ~ncreased eff~ciency of the filter media it is possible to great1y decrease the quant~ty of filter media and thereby ach~eve suff~ciently low res1stance to flow of air in the exhalat~on cycle to obv~ate the need for a separate exhalat;on valve. S~nce resp~ration takes place through the filter med~a dur1ng the lnhalation and exhalation cycles in the respirator of the present ~nvention, the low pressure drop is also experienced on ~nhalation, resulting in a truly comforta-ble l~ghtwe~ght respirator.
The respirator of the present invention in the embodlment shown in the drawings ls totally disposable. An mportant advantage real~zed by a disposable respirator resides in the fact that ît can be dlscarded after use thereby avoid-lng the rlgorous ma1ntenance program for resplrators dicta~ed by the governmental regulations pertaining to worker safety (See for example, 30 CFR Part 11, Subpart A, Section 11.2-1 and 29 CFR Part 1910, Subp~rt I, Sectlon 1910.134~.
It ~s to be understood that although the present lnventlon ls malnly described in terms of disposable chemical cartrldge resplrators, other forms of resplrators are con-templated as coming wlthin the scope of the present inventlonO
~74SZ
Breakthrough tests were conducted on identical respirators, ut~liz~ng a Mechan1cal Breathing Machine con-structed according to speciflcations set forth in A~MoA~
Archives of Industrial Health, Vol. 13, ppO 561-566, 1956.
The tests set forth 1n 30 CFR Part 11 were modified as des-cribed below to permlt testing of the respirators flrst in the conventional manner (when exhalat~on bypasses the chemi-cal cartridge) and second, according to the present invention where exhalation is accomplished through the chemical car-tridge.
A bench test for chemical cartridge respiratorsfor vinyl chloride monomer is set forth in 30 CFR Part 11, Subpart N, Sectlon 11.200-8. It states that an equili-bration atmosphere of 85 + 5% relative humidity and 25 + 5Co will enter the cartridge continuously at 25 lpm for 6 hours.
Next, a test atmosphere of 85 ~ 5% relative humidity and 25 + 5~C. will enter the cartridge continuously at 64 lpm : and 10 ppm of YCM and that, to merit approval, the cartridge should have a m~nimum life of 120 minutes to the penetratlon of 1 ppm of VCM.
The bench test for single use dust respirators set forth in 30 CFR Part 11, Subpart K, Section 11.140-5 states that 40 liters of air per minute w~ll be cycled through the respirator by a breath~ng machine at the rate of 24 resp~rations per m~nute, using a cam having a work rate of 622 kgO-m2/minute. Air exhaled through the respira-tor is required to be at 35 + 2-C. (95 + 3F.) and 94 + 3%
relat7ve hum~d~tyD
Since the valveless, chemlcal cartridge type ~rganic vapor respirator of the present invention depends up~n desorptlon of the contaminant from the filter media durlng exhalatlon to extend its llfetlme over that of a 1~7~52 conventfonal valved respirator, meanlngful bench testing can be accompl;shed only by cycling airflow with a breathing machine. The bench test consists essentially of a combina-tion o~ the two bench tests described above, i.e., cycling the VCM atmosphere descr1bed in 30 CFR Part 11, Subpart N, Section 11.200-8 through the respirator by means of the breathing machine described in 30 CFR Part 11, Subpart K, Section 11L14O-5. The minimum life of the cartridge is the number of minutes measured to the detection of 1 ppm VCM
penetration. Since the breathing machine airflow volume is 0 lpm rather than 64 lpm, the minimum acceptable life for the cartridge was calculated to be: (40) x (120 minutes) or 192 m-nutesO
In the test, a respirator is mounted in a large chamber through which a large volume of 25C. air containing 10 ppm VCM at 85% relative humidity is continuously added and exhausted. A rubber hose was used to provide an air-tight seal between the respirator cartridge mounting device and the breathing machine. A Process Analyzer Incorporated Total Hydrocarbon Analyzer removes 90 cc./min~ from the inhalation a~r and continuously measured the VCM concentra-t~on, the analyzer is callbrated for VCM and has a minumum sensitlvity of 0.1 ppm. At various intervals the same analyzer ls used to measure the chamber concentration to nsure that the 10 ppm VCM challenge is maintained.
The test atmosphere is produced by flowing a measured amount of vlnyl chloride gas into the airflow. The 85% relatlve humidity is maintained by flowing dry a~r through a contalner of heated water.
The temperature and humidity of the exhaled alr are continuously monitored wlth a wet bulb - dry bulb hydrometer to insure 95 + 3F. and 94 ~ 3% relative humidlty.
''- : ' :
~`;
~74SZ
Thls temperature and humidity are generated by passing the exhaled air through a long heated glass tube into which water is added at a constant rate. The temperature and humidity are controlled by varylng the temperature of the tube walls and by varying the water addition rate.
When testing the respirator in the conventional valved manner (where exhalation bypasses the chemical cartrid~e), the exhaled a~r from the breathing machine is vented to the atmosphere.
Following the above described modified NIOSH VCM
certificat~on test with the breathing machine substituted, the respirator demonstrates a service life of 295 minutes, wh~ch greatly exceeds the mlnimum accepted life ¦corrected tlme) of l92 minutes. The 295 minutes service life cor-responds to a comparable valved service life of 30 minutes.
Under the mod1fied NIOSH (breathing machine) conditions, indicator color change is complete at 256 minutes for the 1% MnO2-0055% KMnO4 lndicator. Complete color change means there is no visually perceptible purple remaining in the indlcator bedO It ls believed that an indicator life of approxlmately 90~ of service llfe, which is within the NIOSH
required 80 + 10%, is especially reasonable and realistic s1nce a user does not normally subject a respirator to water vapor equil~brat~on pr10r to usage but rather uses the respirator in the "as received" conditlon. A respirator, tested according to the NIOSH VCM certification test with a breath~ng machine substituted, and without prior water vapor equilibrat~on, was found to have its l ppm service l~fe extended to 480 mlnutes while the indicator showed a c~mplete colcr change at 232 minutesO This is an lndicator life of approximately 50~ of service life.
7 ~ ~2 It will be noted that the indicator of the present invention is an intrins;c part of the sorbent bed. It samples a true corss-section of the atmosphere experienc~d by the sorbent bedO It is n~t a small window Dn the side of an opaque canister which tells the user when a given concen-trat;on has reached the sorbent depth where the window is located. This window approach 75 the one taken by the patentee of United States Patent No. 3,966,440.
It will also be noted that the indicator is located at the entrance of the sorbent bed rather than at the exit.
An indicator located at the entrance of the sorbent bed is exposed to the test atmosphere (10 ppm of vinyl chloride) for the entire t~me interval of the testO
On the other hand, if the indicator is at the exit, ft is exposed only to that amount of VCM which has penetrated the sorbent bed. Tests have shown that the coating weight of KMnO4 on the lndicator granules must be varied depending on the amount of VCM expected to be experienced during testingO This is confirmed by the fact that an entrance located 0% MnO2-0.1~ KMnO4 indicator changes color completely ln 257 minutes in the equilibrated NIOSH tests whereas an ldentical ind~cator in an exit location changes color completely in 620 minutesO This is, of course, long after the respirator has falledO Since an exit located indicator ls exposed to only about 1/20 the amount of VCM as an entrance located indicator over a 257 minute test period, decreasing the KMnO4 coating weight to the level where color change would be expected to be complete in 257 minutes, iOeO, 0% MnO2-0002% KMnO4 or lower, results in an indicator having no visually perceptible colorO
An added advantage realized in an entrance located fndicator is that it samples only the vapor in the inhaled ` ~
D7~52 airO Potassium permanganate on alumina oxidizes most organic vaporsO The exhaled breath contalns many organic vapors, particularly after the user has ingested an organic chemicalO
An entrance-located indicator is protected from chemicals ln the breath by the carbon sorbent bed.
RESPIRATOR
The present invent~on relates to valveless chemlcal cartrldge resplrators for filtratlon of vinyl chlor~de monomer (VCM) and hav~ng an end of service life indlcator as an integral par~ thereofO So far as ~s known, all commercially avallable ~.
chem~cal cartrldge resplrators are equipped with inhalation and exhalat~on valvesO Inhalation valves prevent exhaled alr from entertng the oartridge and contam~nating the filter media w7th excess humid~tyO Exhalat~on valves permit easier exhalatlon slnce the res~stance to flow of air therethrough ~s very lowO
The prlor art, ~ncluding various governmental agencies, has treated as lnv~olable fact that respirators for toxic vapors and gases must be equipped with lnhalatlon and exhalation valves to be ef~ect1veO Thus, reference to Subpart L of Part ll of ~ S~bchapter B of Chapter l, Title 30, Code of Federal Regula-: t10ns, Federal Reg~ster, VolO 37, NoO 59, March 25, 1972, and Subpart N, Federal Reg1ster, Yol. 39, No. 251, December 30, 1974, (hereafter to be referred to as 30 CFR Part ll, Subpart and Sectlon) wlll conf~rm the fact that approval of chem~cal cartr~dge resp~rators ~s predicated on structures : contaln~ng inhalat~on and exhalation valvesO The Austral~an Standards CZll and Zl8-1968 for "Resplratory Protectlve Dev~ces" and Brlt~sh Standard BS 2091:1969 for "Respirators : for Protect~on Against Harmful Dusts and Gases" are slm11arly prem~sed.
; The present 1nvent~on relates to long-llfe valveless chemical cartrldge resplrators ~or vinyl chloride monomer and 1s intended for uses where approval by the Minlng Enforcement and Sa~ety Administratlon or the National Institute of Occu-pational Saf`ety and Health ~NIOSH) would be requiredO
It was early recogn7zed that any respirator for vinyl chlorlde ~onomer would requlre approval ~rom the pertlnent regulatory agency in order to be a vidble commerclal ''~
~
``` ~1~17~Z
productO The requirements for NIOSH approval of a vinyl chlorlde resplrator are found in 30 CFR Part 11, Subpart N, Sections 11-200 through 11-2080 Under these regulations, a vlnyl chlorlde respirator must last at least 120 m7nutes before 7 ppm VCM penetrates the cartr~dgeO Accordingly, although cons~derable effort was expended ~n attempts to meet the appllcable standards for cartrldge type respirators by us7ng a wide variety of commercially ava~lable carbons in a test cartridge with d~mensions approximating a chemical cartridge for a resp~rator, no carbon was found which lasted more than 70 minutes when tested under the condit~ons prescribed ln Subpart N~ Sectlon 11-203. Other efforts were directed to different media formulatlons and cartridge configuratl3nsO
It was then d1scovered that by the seemingly s~mple exped~ent of el~m~natlng the ~nhalation and exhalation valves o~ the known prlor art chemical cartridge resplrators, low pressure-drop valveless f~lter-type respirators hav~ng break-through t~mes to toxic vapors and gases at least double the breakthrough t~mes of conventlonal valved resp~rators utillzlng identlcal chemical cartridges were obtained. Addltlonally, it was found that, dependlng on the type of carbon utlllzed, the amount of ~ilter media in the resplrator could be reduced lo about 50% or less of the p~ev~ously "required" amount thus maklng ~t posslble to greatly reduce the slze and weight of the chemlcal cartr~dge, resulting in a lighter and more comfortab7e respirator~
There st111 remained the necesslty of providlng an end of service l~fe 7nd~cator 7n order for the respirator to ~ualify for approval under the above noted governmenta7 standardsO An extremely rellable yet exceed1ngly s~mple end of servlce llfe indlcator which undergoes a dramatic and d~st~nct colo~ change has now been d~scoveredO
~1~74S2 According to:the present invention, there is provided a disposable valveless chemical cartridge respirator for filtration of vinyl chloride monomer comprising a body including a facepiece having means for peripherally sealing contact with at least that portion of a human head which includes the nose and mouth, associated fastening means for holding said respirator in position on the head, a cartridge on said body having an air entrance and an air exit communicating with the interior of said respirator and contain-ing therewithin filter media comprising activated carbon and an end of service life indicator, said cartridge having a volume of about 220 cc. for said indicator and said filter media, said indicator being disposed across the path of air intake at the entrance of said cartridge, said filter media and indicator being adapted for adsorption thereon of a vinyl chloride monomer contaminant upon inhalation therethrough, said indicator including means upon exposure to a predetermined amount of vinyl chloride monomer undergoing a dramatic and distinct color change to indicate the end of service life o said respirator.
-2a-i74~;2 In the accompanying drawing which illustrates the nvention:
Flgure l ls a front eleYational view of a chemical cartridge resp~rator embodylng the principles of the present tnventlon, and -F1gure 2 is an enlarged view ,partly in section,of the respirator of F~gure l.
Referring more particularly to Figure 1 of the drawlng, lO denotes a valveless cartridge respirator comprising a transparen~ molded plastic body ll of a generally pear-shaped contour and having an inwardly turned marginal lip or edge portion to provide an air-tight seal. Chemical cartridge 20 is formed as an integral part of body ll and comprises a shallow, generally cylindroid molded transparent plastic container 21 prov~ded with openings 12 to form a mesh for air passage~ Cartri~ge 20 has a volume of about 220 cc. for the indicator and fflter media ~sorbent). Starting from the front or left as viewed in F~gure 2, the cartridge 20 contalns a nonwoven retainer web 22, 30 cc. of indicator 23, l90 ccO of activated carbon 24 and a second nonwoven retainer web 250 A molded mesh plate 26 is welded to the back of cartridge 20 to hold the contents tightly in placeO A molded, polymeric facepiece 27 and sultable headbands 13 are laid in place inside a crimping llp 28 forming the per7phery at body ll.
The lip ls heated, crlmped, and upon cooling tlghtly holds the facepiece 27 and bands 13 in placeO The respirator lO
may, if deslred, be equipped wtth a speaking diaphragm ~not shown)c The lnd1cator of the present inventlon comprises spec~ally prepared activated alumina granules coated flrst from a 1% so7ution of KMnO4, which is then reduced to what ts belie~ed to be MnO2, and then coated from a 0O55~ solution of potassium permanganate. The indicator is viewed through the side wall of the cartridge all along the edge nearest the entrance to the cartridgeO The init~al color is a light purple or purple-pink, hereina~ter referred to as purple for simplicity. Upon exposure to vinyl chloride, the potassium permanganate is reduced to manganese dioxide such that there is a slow, continuous color change from the purple to a light brown or tan-beige (hereafter referred to as brown), the color of manganese dioxide.
The indicator of the present invention is prepared by first coating alumina granules with potassium permanganate whlch is then reduced to the brown manganese dioxide which acts as a partial screen and color enhancer for` the final coating of potassium permanganate. The brown MnO2 coating on the granules acts as a color screen to hide some of the purple of the KMnO4.
The more brown MnO2 present, the more purple KMnO4 is covered upO
Thus, for any given indicator life (modified NIOSH VCM test conditions), say 260 minutes, one must adjust the KMnO4 coating concentration for a given MnO2 coating concentration so that the indicator is visually brown at the end of the period. For any MnO2 concentration (greater than zero), there will be some resi-dual purple KMnO4 left on the indicator granule at the end of the indicator life but it will be visuall~ screened out by the brown MnO2. Thls is illustrated by the fact that an indicator sample coated from a 1% manganese d1oxide solution and a 0.55%
potassium permanganate solution results in an indicator life of 256 minutes, about the same life as the indicator coated from 0%
manganese dioxide and a 001% KMnO4 solution. The 0% MnO2 - 0.1%
KMnO4 lndlcator ~s very llght pink in color and changes only s11ghtly to a l1ght cream color when spent. On the other hand, the 1% MnO2 - 0055% KMnO4 ind7cator changes quite dramatically from the starting purple to the endpoint brown colorO The color contrast from start to f~nish for the latter is much greater and 7~52 the~eby makes the indlcator much easier for the user to read.
The ~ollow~ng table shows several lndlcator samples:
%KMnO4 on MnO2 solutlon KMnO4 solutlon granule Indicator conoentrat70n concentrat~on (by wel~ht) llfe (m~nutes) 0% 0O1% 0.036 257 1.0% 0O35% 0.134 220 lu0% 0~55% 0.228 256 1O0% 0O70% 0.352 330 lo25% 0.55% 0.231 180 1025% 0.80% 0.476 333 The 7nd;cator ~s made by preparing a solut1on of known concentratlon of potass~um permanganate in waterO Activated alum~na granules in a s~ze range of 8 to 14 mesh, avallable from Reynolds Chem~cal Products, is immersed in the solution untll the solutlon has absorbed onto the alumina granules to its equilibrlum level. Excess solut1On is drained off and the granules are dried at about 230F. (105C.) under vacuum with rotation. The coated granules are heated to about 500F. (288~C.) at atmospheric pressure for a period of time necessary to reduce the potassium permanganate to manganese~d1oxlde. A second solution of known concentration of potassium permanganate ln water is prepared. The manganese dlox1de coated alumina granules are immersed in the solution untll the absorptlon reaches an equilibrium levelO The excess solutlon is drained off and the granules are again dried at about 230~F~ (105C.~ under vacuum wlth rotationO
As noted hereinabove, prlor workers in the chemical cartridge type resplrator art have considered inhalation and exhalatlon valves to be essential for proper respirator func-tionlng~ Inhalatlon valves were thought to be necessary to avold contaminating the filter medla with excess1ve humldity, siJnce ~t was "known" that the adsorption cdpacity of the fllter med~a was detrlmentall~ af~ected by h~gh humld~ty, especlally ~elatlve hum~d~t~es abo~e 50%O Exhalatlon valves were, of 17~S2 course, necessary to enable respiration to take p1ace since one could not exhale through the f~lter medla with the inhalation valve ln place. In add~t~on, the exhalatlon valves were deslgned such tha~ the reslstance to flow of air therethrough was very low~
It has now been discovered that any deleterious effect on the fllter med~a caused by the high humidity of exhaled a1r is more than offset by the apparent desorption of the contamlnant from the ~lter media, such that the breakthrough tlme of the filter med~a in a valveless respirator is at least doubled over a conventional valved respirator. Because of this ~ncreased eff~ciency of the filter media it is possible to great1y decrease the quant~ty of filter media and thereby ach~eve suff~ciently low res1stance to flow of air in the exhalat~on cycle to obv~ate the need for a separate exhalat;on valve. S~nce resp~ration takes place through the filter med~a dur1ng the lnhalation and exhalation cycles in the respirator of the present ~nvention, the low pressure drop is also experienced on ~nhalation, resulting in a truly comforta-ble l~ghtwe~ght respirator.
The respirator of the present invention in the embodlment shown in the drawings ls totally disposable. An mportant advantage real~zed by a disposable respirator resides in the fact that ît can be dlscarded after use thereby avoid-lng the rlgorous ma1ntenance program for resplrators dicta~ed by the governmental regulations pertaining to worker safety (See for example, 30 CFR Part 11, Subpart A, Section 11.2-1 and 29 CFR Part 1910, Subp~rt I, Sectlon 1910.134~.
It ~s to be understood that although the present lnventlon ls malnly described in terms of disposable chemical cartrldge resplrators, other forms of resplrators are con-templated as coming wlthin the scope of the present inventlonO
~74SZ
Breakthrough tests were conducted on identical respirators, ut~liz~ng a Mechan1cal Breathing Machine con-structed according to speciflcations set forth in A~MoA~
Archives of Industrial Health, Vol. 13, ppO 561-566, 1956.
The tests set forth 1n 30 CFR Part 11 were modified as des-cribed below to permlt testing of the respirators flrst in the conventional manner (when exhalat~on bypasses the chemi-cal cartridge) and second, according to the present invention where exhalation is accomplished through the chemical car-tridge.
A bench test for chemical cartridge respiratorsfor vinyl chloride monomer is set forth in 30 CFR Part 11, Subpart N, Sectlon 11.200-8. It states that an equili-bration atmosphere of 85 + 5% relative humidity and 25 + 5Co will enter the cartridge continuously at 25 lpm for 6 hours.
Next, a test atmosphere of 85 ~ 5% relative humidity and 25 + 5~C. will enter the cartridge continuously at 64 lpm : and 10 ppm of YCM and that, to merit approval, the cartridge should have a m~nimum life of 120 minutes to the penetratlon of 1 ppm of VCM.
The bench test for single use dust respirators set forth in 30 CFR Part 11, Subpart K, Section 11.140-5 states that 40 liters of air per minute w~ll be cycled through the respirator by a breath~ng machine at the rate of 24 resp~rations per m~nute, using a cam having a work rate of 622 kgO-m2/minute. Air exhaled through the respira-tor is required to be at 35 + 2-C. (95 + 3F.) and 94 + 3%
relat7ve hum~d~tyD
Since the valveless, chemlcal cartridge type ~rganic vapor respirator of the present invention depends up~n desorptlon of the contaminant from the filter media durlng exhalatlon to extend its llfetlme over that of a 1~7~52 conventfonal valved respirator, meanlngful bench testing can be accompl;shed only by cycling airflow with a breathing machine. The bench test consists essentially of a combina-tion o~ the two bench tests described above, i.e., cycling the VCM atmosphere descr1bed in 30 CFR Part 11, Subpart N, Section 11.200-8 through the respirator by means of the breathing machine described in 30 CFR Part 11, Subpart K, Section 11L14O-5. The minimum life of the cartridge is the number of minutes measured to the detection of 1 ppm VCM
penetration. Since the breathing machine airflow volume is 0 lpm rather than 64 lpm, the minimum acceptable life for the cartridge was calculated to be: (40) x (120 minutes) or 192 m-nutesO
In the test, a respirator is mounted in a large chamber through which a large volume of 25C. air containing 10 ppm VCM at 85% relative humidity is continuously added and exhausted. A rubber hose was used to provide an air-tight seal between the respirator cartridge mounting device and the breathing machine. A Process Analyzer Incorporated Total Hydrocarbon Analyzer removes 90 cc./min~ from the inhalation a~r and continuously measured the VCM concentra-t~on, the analyzer is callbrated for VCM and has a minumum sensitlvity of 0.1 ppm. At various intervals the same analyzer ls used to measure the chamber concentration to nsure that the 10 ppm VCM challenge is maintained.
The test atmosphere is produced by flowing a measured amount of vlnyl chloride gas into the airflow. The 85% relatlve humidity is maintained by flowing dry a~r through a contalner of heated water.
The temperature and humidity of the exhaled alr are continuously monitored wlth a wet bulb - dry bulb hydrometer to insure 95 + 3F. and 94 ~ 3% relative humidlty.
''- : ' :
~`;
~74SZ
Thls temperature and humidity are generated by passing the exhaled air through a long heated glass tube into which water is added at a constant rate. The temperature and humidity are controlled by varylng the temperature of the tube walls and by varying the water addition rate.
When testing the respirator in the conventional valved manner (where exhalation bypasses the chemical cartrid~e), the exhaled a~r from the breathing machine is vented to the atmosphere.
Following the above described modified NIOSH VCM
certificat~on test with the breathing machine substituted, the respirator demonstrates a service life of 295 minutes, wh~ch greatly exceeds the mlnimum accepted life ¦corrected tlme) of l92 minutes. The 295 minutes service life cor-responds to a comparable valved service life of 30 minutes.
Under the mod1fied NIOSH (breathing machine) conditions, indicator color change is complete at 256 minutes for the 1% MnO2-0055% KMnO4 lndicator. Complete color change means there is no visually perceptible purple remaining in the indlcator bedO It ls believed that an indicator life of approxlmately 90~ of service llfe, which is within the NIOSH
required 80 + 10%, is especially reasonable and realistic s1nce a user does not normally subject a respirator to water vapor equil~brat~on pr10r to usage but rather uses the respirator in the "as received" conditlon. A respirator, tested according to the NIOSH VCM certification test with a breath~ng machine substituted, and without prior water vapor equilibrat~on, was found to have its l ppm service l~fe extended to 480 mlnutes while the indicator showed a c~mplete colcr change at 232 minutesO This is an lndicator life of approximately 50~ of service life.
7 ~ ~2 It will be noted that the indicator of the present invention is an intrins;c part of the sorbent bed. It samples a true corss-section of the atmosphere experienc~d by the sorbent bedO It is n~t a small window Dn the side of an opaque canister which tells the user when a given concen-trat;on has reached the sorbent depth where the window is located. This window approach 75 the one taken by the patentee of United States Patent No. 3,966,440.
It will also be noted that the indicator is located at the entrance of the sorbent bed rather than at the exit.
An indicator located at the entrance of the sorbent bed is exposed to the test atmosphere (10 ppm of vinyl chloride) for the entire t~me interval of the testO
On the other hand, if the indicator is at the exit, ft is exposed only to that amount of VCM which has penetrated the sorbent bed. Tests have shown that the coating weight of KMnO4 on the lndicator granules must be varied depending on the amount of VCM expected to be experienced during testingO This is confirmed by the fact that an entrance located 0% MnO2-0.1~ KMnO4 indicator changes color completely ln 257 minutes in the equilibrated NIOSH tests whereas an ldentical ind~cator in an exit location changes color completely in 620 minutesO This is, of course, long after the respirator has falledO Since an exit located indicator ls exposed to only about 1/20 the amount of VCM as an entrance located indicator over a 257 minute test period, decreasing the KMnO4 coating weight to the level where color change would be expected to be complete in 257 minutes, iOeO, 0% MnO2-0002% KMnO4 or lower, results in an indicator having no visually perceptible colorO
An added advantage realized in an entrance located fndicator is that it samples only the vapor in the inhaled ` ~
D7~52 airO Potassium permanganate on alumina oxidizes most organic vaporsO The exhaled breath contalns many organic vapors, particularly after the user has ingested an organic chemicalO
An entrance-located indicator is protected from chemicals ln the breath by the carbon sorbent bed.
Claims (6)
1. A disposable valveless chemical cartridge respira-tor for filtration of vinyl chloride monomer comprising a body including a facepiece having means for peripherally sealing contact with at least that portion of a human head which in-cludes the nose and mouth, associated fastening means for hold-ing said respirator in position on the head, a cartridge on said body having an air entrance and an air exit communicating with the interior of said respirator and containing therewithin filter media comprising activated carbon and an end of service life indicator,said cartridge having a volume of about 220 cc.
for said indicator and said filter media, said indicator being disposed across the path of air intake at the entrance of said cartridge, said filter media and indicator being adapted for adsorption thereon of a vinyl chloride monomer contaminant upon inhalation therethrough, said indicator including means upon exposure to a predetermined amount of vinyl chloride mon-omer undergoing a dramatic and distinct color change to in-dicate the end of service life of said respirator.
for said indicator and said filter media, said indicator being disposed across the path of air intake at the entrance of said cartridge, said filter media and indicator being adapted for adsorption thereon of a vinyl chloride monomer contaminant upon inhalation therethrough, said indicator including means upon exposure to a predetermined amount of vinyl chloride mon-omer undergoing a dramatic and distinct color change to in-dicate the end of service life of said respirator.
2. A disposable valveless chemical cartrige respira-tor according to claim 1 wherein said indicator comprises activated alumina granules in a size range of 8 to 14 mesh coated with potassium permanganate, said color change being from pink to light cream.
3. A disposable valveless chemical cartridge respira-tor according to claim 1 wherein said indicator comprises activated alumina granules having a first color enhancing coat of manganese dioxide overcoated with a second color coat of potassium permanganate, said color coat of said indicator upon exposure to a predetermined amount of vinyl chloride monomer being reduced to manganese dioxide such that there is a slow, continuous color change from purple to brown to indicate the end of service life of said respirator.
4. A disposable valveless chemical cartridge respira-tor according to claim 3 wherein said filter media and indicator are contained in a cartridge integrally formed as part of the respirator body.
5. A disposable valveless chemical cartridge respirator according to claim 4 containing about 190 cc. of activated carbon and about 30 cc. of indicator granules, said respirator upon exposure to an atmosphere containing 10 parts per million of vinyl chloride gas having a breakthrough time to one part per million of vinyl chloride gas of about 295 minutes and an end of service life indicator color change time of about 256 minutes.
6. A disposable valveless chemical cartridge respirator according to claim 4 wherein said indicator granules are disposed in a layer located at the entrance of said car-tridge.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US750,266 | 1976-12-13 | ||
| US05/750,266 US4155358A (en) | 1976-12-13 | 1976-12-13 | Respirator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1107452A true CA1107452A (en) | 1981-08-25 |
Family
ID=25017147
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA289,674A Expired CA1107452A (en) | 1976-12-13 | 1977-10-27 | Respirator |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4155358A (en) |
| CA (1) | CA1107452A (en) |
| DE (1) | DE2755966A1 (en) |
| GB (1) | GB1597979A (en) |
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| US4326514A (en) * | 1980-06-20 | 1982-04-27 | Minnesota Mining And Manufacturing Company | Cartridge respirator with service life indicator |
| US4488547A (en) * | 1982-09-07 | 1984-12-18 | Kenneth R. Bowers, Jr. | Face mask |
| DE3445639A1 (en) * | 1984-12-14 | 1986-06-26 | Drägerwerk AG, 2400 Lübeck | COLORIMETRIC INDICATOR TO INDICATE THE EXHAUST OF GAS FILTERS |
| US5062421A (en) * | 1987-11-16 | 1991-11-05 | Minnesota Mining And Manufacturing Company | Respiratory mask having a soft, compliant facepiece and a thin, rigid insert and method of making |
| US4928687A (en) * | 1988-10-11 | 1990-05-29 | The University Of Florida | CO2 diagnostic monitor |
| US5156159A (en) * | 1988-10-11 | 1992-10-20 | University Of Florida | CO2 diagnostic monitor with rupturable container |
| CA2020503C (en) * | 1990-07-05 | 1998-11-17 | Jacques Lesage | Chemical cartridge for protective respiratory mask |
| US5212131A (en) * | 1991-02-20 | 1993-05-18 | Innovative Research Enterprises | Low pressure drop filter |
| US5383469A (en) * | 1992-01-31 | 1995-01-24 | Board Of Trustees Of The Leland Stanford Junior University | Neonatal hemolysis detection using end-tidal breath sampler and analyzer apparatus |
| TW284848B (en) * | 1992-06-05 | 1996-09-01 | Supelco Inc | |
| WO1995012432A1 (en) * | 1993-11-05 | 1995-05-11 | Purecab Australia Pty. Ltd. | Respiratory filter indicator |
| US6004522A (en) * | 1993-12-15 | 1999-12-21 | Purafil, Inc. | Solid filtration media incorporating elevated levels of permanganate and water |
| TW287952B (en) * | 1994-08-31 | 1996-10-11 | Lifepro Inc | |
| US5964218A (en) * | 1994-08-31 | 1999-10-12 | Lifepro, Inc. | Face mask with back-up smoke inhalation protection and method of operation |
| US5942323A (en) * | 1995-01-27 | 1999-08-24 | Purafil, Inc. | Fiber filter and methods of use thereof |
| NL1004343C2 (en) * | 1996-10-23 | 1998-04-24 | Tno | Device for removing from one gas or vapor mixture one or more substances or dangerous substances undesirable for humans, and a gas mask comprising such a device. |
| US6186140B1 (en) | 1997-03-14 | 2001-02-13 | 3M Innovative Properties Company | Respiratory filter element having a storage device for keeping track of filter usage and a system for use therewith |
| US6152990A (en) * | 1999-02-04 | 2000-11-28 | Engelhard Corporation | Device for removing and retaining volatile compounds and method of employing the same |
| US6290713B1 (en) | 1999-08-24 | 2001-09-18 | Thomas A. Russell | Flexible illuminators for phototherapy |
| US6497756B1 (en) | 2000-09-12 | 2002-12-24 | North Safety Products, Inc. | Service life indicator for respirator cartridge |
| CA2456216C (en) * | 2001-08-10 | 2008-07-22 | North Safety Products Inc. | Respirator |
| EP1439892A2 (en) | 2001-10-02 | 2004-07-28 | Scentczar Corporation | Residual life indicator |
| ITMI20020406U1 (en) * | 2002-08-30 | 2004-02-29 | Stefanoni Roberto | UNIVERSAL COVER FOR ABSORBENT AND FILTERING VAPOR AND ODOR POT |
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| WO2005063326A1 (en) * | 2003-12-31 | 2005-07-14 | Resmed Limited | Mask system |
| US8104472B2 (en) | 2004-03-26 | 2012-01-31 | 3M Innovative Properties Company | Non-elastomeric respirator mask that has deformable cheek portions |
| US7442237B1 (en) * | 2004-09-16 | 2008-10-28 | The United States Of America As Represented By The Secretary Of The Army | Multi-agent end-of-service-life indicator for respirator filters |
| US20060254592A1 (en) * | 2005-01-28 | 2006-11-16 | Bruce Anders | Respiratory mask |
| US7503962B2 (en) * | 2005-12-16 | 2009-03-17 | Attar Amir J | End of service and residual life indicator |
| US20070251522A1 (en) * | 2006-05-01 | 2007-11-01 | Welchel Debra N | Respirator with exhalation vents |
| US20100224199A1 (en) * | 2006-05-01 | 2010-09-09 | Kimberly-Clark Worldwide, Inc. | Respirator |
| US8067110B2 (en) * | 2006-09-11 | 2011-11-29 | 3M Innovative Properties Company | Organic vapor sorbent protective device with thin-film indicator |
| US20090044811A1 (en) * | 2007-08-16 | 2009-02-19 | Kimberly-Clark Worldwide, Inc. | Vent and strap fastening system for a disposable respirator providing improved donning |
| US20090044809A1 (en) * | 2007-08-16 | 2009-02-19 | Kimberly-Clark Worldwide, Inc. | Vent and strap fastening system for a disposable respirator |
| US9642403B2 (en) * | 2007-08-16 | 2017-05-09 | Kimberly-Clark Worldwide, Inc. | Strap fastening system for a disposable respirator providing improved donning |
| US8328903B2 (en) * | 2008-05-30 | 2012-12-11 | Scott Technologies, Inc. | Determining effluent concentration profiles and service lives of air purifying respirator cartridges |
| WO2010002575A2 (en) * | 2008-06-30 | 2010-01-07 | 3M Innovative Properties Company | Exposure indicating device |
| US7860662B2 (en) * | 2008-12-17 | 2010-12-28 | Scott Technologies, Inc. | Systems and methods for determining filter service lives |
| AU2011235303A1 (en) * | 2010-04-02 | 2012-11-01 | 3M Innovative Properties Company | Filter systems including optical analyte sensors and optical readers |
| WO2011156609A2 (en) | 2010-06-09 | 2011-12-15 | Cummins Filtration Ip Inc. | System for monitoring and indicating filter life |
| BR112012020926A2 (en) | 2010-06-17 | 2016-05-03 | Cummins Filtration Ip Inc | method for providing the internal combustion engine user with the economically optimal air filter replacement range |
| GB2542060B (en) | 2010-08-06 | 2017-08-02 | Scott Tech Inc | Method and apparatus for integrating chemical and environmental sensors into an air purification filter through a reusable sensor post |
| CN103119436A (en) | 2010-09-23 | 2013-05-22 | 3M创新有限公司 | Porous chemical indicator for gaseous media |
| US9011584B2 (en) | 2011-08-25 | 2015-04-21 | Honeywell International Inc. | End of service life indicator for respirator |
| US9192795B2 (en) | 2011-10-07 | 2015-11-24 | Honeywell International Inc. | System and method of calibration in a powered air purifying respirator |
| US9808656B2 (en) | 2012-01-09 | 2017-11-07 | Honeywell International Inc. | System and method of oxygen deficiency warning in a powered air purifying respirator |
| US10926051B2 (en) * | 2012-09-21 | 2021-02-23 | Innomed Healthscience, Inc. | Respiratory interface |
| EP2969128B1 (en) | 2013-03-15 | 2018-11-14 | 3M Innovative Properties Company | End of service life indicating systems for layered filter cartridges |
| US10751495B2 (en) | 2013-12-20 | 2020-08-25 | Koninklijke Philips N.V. | Patient interface |
| USD746439S1 (en) | 2013-12-30 | 2015-12-29 | Kimberly-Clark Worldwide, Inc. | Combination valve and buckle set for disposable respirators |
| EP3188612B1 (en) | 2014-09-05 | 2023-07-05 | Honeywell International Inc. | End of service life indicator for disposal mask |
| USD760378S1 (en) * | 2015-01-30 | 2016-06-28 | 3M Innovative Properties Company | Respirator mask face seal |
| US11235181B2 (en) * | 2020-06-05 | 2022-02-01 | The Government of the United States of America, as represented by the Secretary of Homeland Security | Breathable respirator mask with multiple layered filters |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1789262A (en) * | 1928-03-15 | 1931-01-13 | Monro Randolph | Canister |
| US2665686A (en) * | 1952-03-17 | 1954-01-12 | Edwin E Wood | Face mask |
| US3615233A (en) * | 1969-07-28 | 1971-10-26 | Chemetron Corp | Disposable carbon dioxide absorber |
| US3902485A (en) * | 1974-02-08 | 1975-09-02 | Richard A Wallace | Chemically activated warning system |
| US3966440A (en) * | 1975-06-03 | 1976-06-29 | Catalyst Research Corporation | Colorimetric vinyl chloride indicator |
-
1976
- 1976-12-13 US US05/750,266 patent/US4155358A/en not_active Expired - Lifetime
-
1977
- 1977-10-27 CA CA289,674A patent/CA1107452A/en not_active Expired
- 1977-12-12 DE DE19772755966 patent/DE2755966A1/en active Granted
- 1977-12-12 GB GB51682/77A patent/GB1597979A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1597979A (en) | 1981-09-16 |
| US4155358A (en) | 1979-05-22 |
| DE2755966A1 (en) | 1978-07-06 |
| DE2755966C2 (en) | 1988-12-08 |
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| MKEX | Expiry |