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May 6, 1982

Air Purification Lab
U.S. Divers Company
3323 West Warner Avenue
Santa Ana, California 92702

Dear

This is in response to your letter of April 8, 1982, concerning respiratory protection against isocyanate containing paint sprays.

We understand that 3M has not submitted the 8709 or the equivalent valveless Models 8711 or 6984 to NIOSH for testing and approval. However, NIOSH has conducted tests on the 8711 and 8709 respirators and the results indicate that these respirators fail to meet the performance criteria as paint spray respirators.

Our major concern with the use of negative-pressure air purifying respirators for protection against isocyanate containing paints is not that the sorbent may be ineffective, but rather the leakage around the facepiece seal. Since the isocyanates have poor odor warning properties, workers could be constantly exposed to isocyanates which they cannot detect by the odor. The odor would indicate a leak in the face seal or a breakthrough in the sorbent.

Early last year, we were informed by the DuPont Company that they were working to solve the odor warning problems of isocyanates, but we have not received a report from them yet. Since the isocyanates are a potent irritant and sensitizer, the negative-pressure respirators do not provide adequate protection because of possible cartridge breakthrough and an inability to assure efficient enough face sealing.

Thus it is a violation of our standards to use a negative pressure paint spray respirator, whether approved or not, for protection against paint sprays containing isocyanates.

Sincerely,



Patricia Breslin
Deputy Director