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Change Schedule
Experimental Testing
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Conducting Experimental Tests  Conducting Experimental Tests
to determine a cartridge's service life

Probably the best way to determine service life for multiple chemicals or specific conditions.  Some published data from breakthrough studies for organic vapor cartridges have been tabulated here.

Steps Example
1. Obtain the following information:
  • names of all airborne contaminants
  • breathing rate of workers or;
  • maximum flow rate of powered air purifying respirator
  • estimate of worst case exposure levels
Carl is part owner of a carpet manufacturing plant where a third of the employees wear full mask respirators to protect them from trichloroethylene.  They are changing the respirator cartridges about every two hours based on an estimate using a math model. Carl believes the cartridges probably have a longer service life and would like to have more accurate, experimental tests performed.  Because some of the workers perform extremely physical tasks on a regular basis, Carl has identified the breathing rate as very high.
2. Determine who will conduct the experimental tests.
  • Your company's Industrial Hygienist
  • An outside consultant or laboratory
Carl recently contacted a local certified analytical laboratory. He works out a deal with them to have the cartridges tested in their lab.
3. Provide the tester with the following:
  • information from step 1
  • actual cartridges for the respirators
  • the opportunity to test at the work site under typical conditions; or
  • the range of variable factors or conditions to be given to the lab
Carl visits the laboratory and gives some cartridges and the existing data to the lab director, including the maximum relative humidity of the work environment.
4. Obtain the results and create a written change schedule for the cartridges. Carl visited the lab some days later and was pleased to find out that the cartridge protection actually lasted close to 4 hours before the chemical broke through the cartridge! Carl multiplied a safety factor of 3/4 to the estimate and set his change schedule at 3 hours. This meant that he could purchase a third fewer cartridges. Carl took the lab reports and change schedule and incorporated them into his written respirator program.

Keep in Mind Keep In Mind
  • There is no widely accepted, standard protocol for performing service life testing.
  • OSHA has devised a field testing approach which will demonstrate the validity of an established change schedule.
  • The EPA has published draft Interim Recommendations for cartridge testing.
  • A field testing approach is provided by Cohen, H. J., Development of a Field Method for Calculating the Service Lives of Organic Vapor Cartridges – Part IV. Results of Field Validation Trials, American Industrial Hygiene Association Journal, (1991), pages 263-270.
  • Ideally, respirator cartridges should be tested under worst case conditions either in the workplace or in the laboratory.
  • The determination of breakthrough from workplace testing does not require the determination of the full breakthrough curve for the respirator cartridge.

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