Device to indicate the concentration of ethylene oxide in the workplace

• US 4,597,942 A
• Filed: 08/15/1983
• Issued: 07/01/1986
• Est. Priority Date: 05/25/1983
• Status: Expired due to Fees

• Current Assignee: Graphic Controls Canada Limited
• Original Assignee: Graphic Controls Canada Limited
• Inventors: Meathrel, William G.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/523,050
• Time in Patent Office: 1,051 Days
• Field of Search: 73/23, 116/206, 422/55-58, 422/86-88, 422/119, 436/1, 436/93, 436/142, 436/165, 436/167, 436/169, 436/902
• US Class Current: 422/426
• CPC Class Codes: G01N 31/223 for investigating presence of specific gases or aerosols G01N31/221, G01N31/222 take precedence; actuation of fire alarm by presence of smoke or gases G08B17/10
• CPC Class Codes: Y10T 436/142222 Hetero-O [e.g., ascorbic acid, etc.]

Abstract

A visual indicator device and dosimeter in which a liquid crystal composition deposited on an opaque dark-colored carrier substrate undergoes color changes which depend on the concentration, and total quantity, of ethylene oxide to which the device has been exposed. The device serves both to monitor the concentration of ethylene oxide in the environment and to indicate a time-weighted average exposure.

Claims

1. A dosimeter for providing a contemporaneous, on-going visual indication of the total cumulative concentration of ethylene oxide to which a wearer of said dosimeter has been exposed, said dosimeter comprising,

first sensor means responsive to ethylene oxide for enabling a continuous determination of the current concentration of ethylene oxide in an ambient environment,

said first sensor means constituting a control reference area,

gas-absorbing means for extracting, absorbing, retaining and cumulatively integrating ethylene oxide gas concentration present in an ambient environment,

second sensor means in gas-sensing communication with said gas-absorbing means for reacting with ethylene oxide gas absorbed in and concentrated by said gas-absorbing means to permit a cumulative, quantitiative determination of total gas absorbed by said gas-absorbing means, and to indicate a wearer'"'"'s total exposure to ethylene oxide over a time-weighted average,

said first and said second sensor means comprising liquid crystal compositions which exhibit color changes when exposed to ethylene oxide gas and siad first sensor means and said second sensor means being responsive to undergo color changes upon exposure to ethylene oxide whereby temperature effects between the two sensor means are cancelled, and wherein differences in color between said first sensor means and said second sensor means provide a quantitative indication of a concentration of ethylene oxide to which said dosimeter has been exposed.

2. The structure as set forth in claim 1 wherein said gas-absorbing means is selected from the group consisting of activated charcoal, silica gel, alumina, and mixtures thereof.

3. The structure as set forth in claim 1 wherein said liquid crystal compositions include cholesteric esters in combination with a binder selected from the group consisting of gelatin, polyvinyl alcohol, cellulose polymers, latex resins, acrylic resins, and mixtures thereof.

4. The structure as set forth in claim 1 wherein said liquid crystal compositions include cholesteric esters present as an encapsulated phase.

5. The structure as set forth in claim 1 wherein said first and said second sensor means comprise mixtures of cholesteric liquid crystal compositions.

6. The structure as set forth in claim 1 and further comprising attenuating means for controlling diffusion of gas to said second sensor means, said attenuating means being interposed physically between ambient atmosphere and said liquid crystal compositions of said second sensor means.

7. A device for indicating simultaneously and concurrently the concentration of ethylene oxide present in an ambient atmosphere and the total accumulated amount of ethylene oxide to which a wearer of the device has been exposed, said device comprising an assembly including:

a test portion and a control portion;

said test portion comprising substrate means for supporting a liquid crystal coating composition thereon,

a first liquid crystal composition deposited as a coating on said substrate means,

gas-absorbing means for extracting, absorbing, and for retaining of ethylene oxide derived from an ambient environment and for building-up ethylene oxide concentrations in said gas absorbing means,

said gas absorbing means being adhered to said substrate means and being in gas-diffusion communication with said first liquid crystal compositions,

whereby ethylene oxide accumulated in said gas-absorbing means acts upon said liquid crystal composition to effect therein a color change correlated with an accumulated, total exposure of said device to ethylene oxide;

said control portion comprising an ethylene oxide impermeable barrier film,

a second liquid crystal composition coating a top surface of said barrier film, and

means bonding said barrier film of said control portion to overlie said test portion;

said second liquid crystal composition being responsive to ethylene oxide to undergo color changes and to assume a color correlated with existing and with changing concentrations of ethylene oxide present in an ambient environment.

8. The structure as set forth in claim 7 wherein said first liquid crystal composition and said second liquid crystal composition each comprises a mixture of cholesteric liquid crystals and wherein said mixture is the same for each liquid crystal composition.

9. The structure as set forth in claim 7 wherein said assembly comprises a test portion and a control portion which

10. The structure as set forth in claim 7 wherein said assembly comprises a test portion and a control portion which define laterally adjacent and contiguous areas. define overlapping areas.

11. The structure as set forth in claim 7 and further comprising attenuating means for controlling diffusion of ethylene oxide gas to said first liquid crystal composition, said attenuating means being interposed physically between ambient atmosphere and said first liquid crystal composition.