Performance Of Dust Respirators Against A Fibrous Dust

Our plain-English summary of Performance Of Dust Respirators Against A Fibrous Dust, by T.J. Weeks, A.F. Burns (1970).

The study

• Authors: T.J. Weeks, A.F. Burns
• Published: American Industrial Hygiene Association Journal 31(3):290-293, May-June (1970)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 1419. The article is still under copyright, so we describe it here rather than post it.

In plain English

This was a laboratory study testing how well dust respirators held back a fibrous dust. The authors made a test dust by twice micropulverizing and twice air-jet milling Canadian chrysotile asbestos from the Johns-Manville Jeffrey mine. The fibers were generally less than 10 microns long and less than 1 micron in diameter. Eight respirators were tested against this dust using standard Bureau of Mines techniques: three approved by the Bureau of Mines and five not approved. All but one let less than 1% of the fiber through. The authors concluded that the respirators offered considerable protection against asbestos, except perhaps respirator U6. One nonapproved respirator let through 0.57% of the chrysotile, but let through far more silica in the standard silica dust test. The authors stated that there were not yet enough data for any general statement comparing fibrous and particulate dusts. Because chrysotile is a soft, flexible fiber, they said the results may not hold for harsh, brittle fibers such as amosite or crocidolite. They also said more work is needed to set a standard test.

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 test of respirator filtering performance against a prepared fibrous (chrysotile asbestos) test dust in a dust chamber, using standard Bureau of Mines techniques
• Who was studied: Eight dust respirators (three Bureau of Mines approved, five nonapproved), tested at the Bureau of Mines Laboratory in Pittsburgh, Pennsylvania; published 1970
• Exposure: Test dust of Canadian chrysotile asbestos from the Johns-Manville Jeffrey mine, twice micropulverized and twice air-jet milled to mostly respirable size; air was drawn through each respirator at 32 liters per minute
• Main results:
  • With one exception, all eight respirators had fiber breakthrough below 1% (the percent sign is garbled in the scanned abstract; the cover summary page reads 1%)
  • The prepared chrysotile test dust had fibers generally less than 10 microns long and less than 1 micron in diameter
  • A respirator, apparently the nonapproved U4 (the only one also given the standard silica dust test), allowed a chrysotile breakthrough of 0.57%. In the standard silica dust test it allowed a much higher silica breakthrough, printed as 17.2 with the unit garbled
• The authors' conclusion: The authors concluded that the respirators tested offer considerable protection against asbestos, except perhaps respirator U6
• Limitations the authors state:
  • Not enough data had been collected to make any general statement about respirator performance against a fibrous dust as opposed to a particulate dust
  • Chrysotile is a soft, flexible fiber, and the results may not be valid for harsh, brittle fibers such as amosite, crocidolite or a harsh chrysotile
  • Additional work on feed tube size, lift rate and fiber packing is needed before a standard test for respirators against fibrous dust can be established
  • Clumping of fiber in the feed tube could make the dust concentration in the test chamber vary (run 4)

Topics

Medical terms in this study, explained in our Lexicon: Respirator, Chrysotile, Johns-Manville, Jeffrey Mine, Amosite, Crocidolite.

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