Performance of power assisted respirators during simulated asbestos removal

Our plain-English summary of Performance of power assisted respirators during simulated asbestos removal, by M.P. Clayton, A.E. Bailey, N.P. Vaughan, et al (The Annals of Occupational Hygiene, 2002).

The study

• Authors: M.P. Clayton, A.E. Bailey, N.P. Vaughan, R. Rajan
• Journal: The Annals of Occupational Hygiene
• Published: 2002;46(1):49-59
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Protection factors were measured on full face mask power assisted respirators when worn by experienced asbestos removal operatives under simulated asbestos removal work conditions. The sulfur hexafluoride test method as defined in European Standards was employed to determine the leakage into the respirators. Protection factors were measured on a total of 21 test volunteers. The test method allowed protection factors to be related to wearer activities and practices. Poor fitting techniques and simulated reduction in the respirator's performance resulted in a reduction in the protection factor. Visual inspection of the RPE usually worn by the volunteers identified inadequate maintenance. This study re-emphasises that careful selection, facepiece fit testing and correct use and maintenance of RPE are essential to ensure optimum protection to the wearer.

In plain English

This laboratory simulation measured how well full face mask power assisted respirators protected 21 experienced UK asbestos removal workers. No asbestos was used. Volunteers stripped and replaced plaster board in a test chamber the way they would remove asbestos lagging and asbestos insulation board, while leakage of a test gas (sulfur hexafluoride) into the mask was measured. Protection factors, where a higher number means less leakage, were averaged over each whole test. They ranged from 20 000 down to 400, the only result below 2000. Switching the respirator off cut protection by a factor of three on average. Heavy sweating and loose straps also lowered protection, and one volunteer whose mask was not fully secure measured below 50 with the power off. Twenty of the 21 did not use the air flow indicator, none had ever been fit tested, and some of the workers' own masks were poorly maintained or contaminated with asbestos. The authors concluded that with careful selection, fit testing, correct use and maintenance, these respirators can protect above the current assigned protection factor. They noted that simulated results cannot be directly related to workplace performance.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory simulation study measuring respirator protection factors continuously with a sulfur hexafluoride (SF6) test gas, combined with video recording of the work
• Who was studied: 21 experienced asbestos removal workers (strippers) from firms belonging to UK asbestos trade associations; their work experience ranged from 6 months to 22 years (mean 10 years)
• Exposure: No asbestos was used. Volunteers removed plaster board, as they would asbestos lagging and asbestos insulation board, while wearing one of two types (Type A, Type B) of full face mask power assisted respirator with P3 filters, in a chamber filled with SF6 test gas. Some tests included periods with the power switched off, a partly discharged battery, or raised temperature.
• Main results:
  • Mean protection factors over each whole test ranged from 20 000 (test No. 2) down to 400 (test No. 15); test No. 15 was the only one of the 21 tests below 2000.
  • In the 13 tests where the respirator was switched off, protection fell on average by a factor of three, and by a factor of 100 for one volunteer. Ten of the 13 still had a protection factor above 2000.
  • Heavy sweating when the chamber temperature was raised reduced protection. In test No. 9 the protection factor fell from around 3850 to around 550; in test No. 11 it fell from 7700 to 1250.
  • The three volunteers who fitted masks with insufficient tension in any strap (tests 15, 16 and 19) had a mean initial protection factor of 4150, compared with 10 000 for the other users.
  • Volunteer 15, whose mask was still not fully secure, had a protection factor below 50 when the power was switched off to simulate battery failure.
  • 20 of the 21 volunteers did not use the air flow indicator provided.
  • Only three volunteers carried out a negative pressure (suck down) test, and only one did it correctly.
  • None of the volunteers had ever been fit tested for their respirator.
  • On inspection of the volunteers' own respirators, some masks were poorly maintained, some were contaminated with asbestos inside and out, and some were distorted around the face seal.
  • None of the volunteers fitted the respirator exactly as the manufacturer's instructions described, although 7 of 21 fitted their mask in an acceptable way.
  • All overall protection factors in the simulation exceeded the assigned protection factor for this type of respirator, which the article gives as 40.
• The authors' conclusion: The authors concluded that, with careful selection, facepiece fit testing, and correct use and maintenance, power assisted respirators can provide protection above the current assigned protection factor.
• Limitations the authors state:
  • This was a simulation, not a measurement of protection in real workplaces.
  • The method did not measure leakage through the filter, so the measured leakage is not total inward leakage.
  • Being observed probably encouraged the volunteers to use good working practices.
  • The respirators used were in good condition and received good airflow throughout, unlike real jobs where filters clog and batteries weaken.

Topics

Medical terms in this study, explained in our Lexicon: Respirator, Assigned Protection Factor.

Related studies

• Workplace protection factors of HSE approved negative pressure full-facepiece dust respirators during asbestos stripping: preliminary findings — S.N. Tannahill, R.J. Willey, et al. (1990)
• Evaluation of respirator filters for asbestos fibers — Y.S. Cheng, T.D. Holmes, et al. (2006)
• Physiological and subjective responses to working in disposable protective coveralls and respirators commonly used by the asbestos abatement industry — M.K. White, T.K. Hodous, et al. (1989)
• Health effects of respirator use at low airborne concentrations — J.H. Lange (2000)
• Effect of respiratory protective equipment on exposure to asbestos fibres during removal of asbestos insulation — H. Akkersdijk, C.F. Bremmer, et al. (1989)
• A comparative study on the performance of asbestos-free depth-filters for removal of pyrogens from infusion fluids — C. Baggerman, C. Brandsema, et al. (1981)

Browse more research in The Annals of Occupational Hygiene, or return to medical research.