OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at http://www.osha.gov.

May 21, 1986

Mr. Arthur C. Miller, Jr.
Vice President
11428 Kingston Pike
Knoxville, Tennessee 37922

Dear Mr. Miller:

This is in response to your February 6 letter requesting a written opinion from the Occupational Safety and Health Administration (OSHA) concerning the equivalence of the CAM/PCAM Model C instrument to the vertical elutriator (VE) cotton dust sampler as provided in the cotton dust standard 29 CFR 1910.1043(d)(1)(iv).

We have reviewed the data you submitted with your February & request, including the referenced docket documents (Ex. 203 and Ex. 235) and the March 7 Supplementary information regarding the CAM/PCAM method and equivalence date.

The set of data addressed in your letter was a result of three different tests conducted with different employers. It contains 100 samples collected at 10 different sites covering seven different processes. Ten measurements were made at each site with dust levels ranging from 0.39 to 1.92 times the permissible exposure limit (PEL). Measurements from two VEs were averaged. Also, you corrected the CAM/PCAM results by applying the Gravimetric Certification (GC) and Equivalence Refinement Factor (ERF) procedures. The Rockette/Wadsworth equivalence protocol calculation procedure was followed and the critical T value was determined.

OSHA acknowledged in the preamble to the cotton dust standard that mills may have dust levels two times the PEL after March 1984. Additionally, OSHA believes that testing above the PEL in a laboratory or other experimental setting reasonably modeled after a mill in appropriate. Therefore, although the data came from different mills and were collected several years ago, we are accepting these data because they fulfill the 0.5 to 2 times the PEL requirement of the equivalence protocol.

The GC and ERF procedures are described in a paper "Gravimetric Certification and Equivalence Demonstration Protocols for Alternative Samplers to the Elutriator" of Ex. 203. In this paper, it is stated that the GC procedurewas used to assure proper calibration of the individual CAM and PCAM sensors, that the ERF provides a small correction to the CAM readings, and that both the GC and the ERF procedures constitute an integral part of the CAM method.

The calculated critical value (T.68.71) based on the data collected using the GC and ERF procedures is less than 25 percent of the vertical elutriator average (261.69 x 0.25 x 70.42). Consequently, the February 6 equivalence data of the CAM/PCAM Model C have met the requirements of the Rockett/Wadsworth equivalence protocol.

Therefore, pursuant to 29 CFR 1910.1043(d)(1)(iv), based upon all the information and data you submitted, and your certification that the information, data, and producers described in Ex. 203 are accurate, it is OSHA's opinion that the CAM/PCAM Model C instrument is equivalent to the vertical elutriator if the GC and ERF procedures are applied. Since the equivalence was demonstrated using the GC and ERF corrected results, the equivalence is valid only if the users of the CAM/PCAM Model C instrument apply the GC and ERF procedures during sampling.


Edward J. Baier
Directorate of Technical Support

February 6, 1986

Mr. Patrick R. Tyson
Acting Assistant Secretary
Occupational Safety and
Health Administration
200 Constitution Avenue N.W.
Washington, DC 20210

Dear Mr. Tyson:

We are requesting the written opinion concerning the equivalence of the CAM/PCAM Model C instrument to the vertical elutriator from paragraph [d] [l] [iv] in the 29 CFR 1910 Final Rule on the Occupational Exposure to Cotton Dust, December 13, 1985. The enclosed information and data show that the CAM/PCAM Model C cotton dust sampler collects particulates in the same range as the vertical elutriator and satisfies the equivalence protocol published in Appendix E of the amended 1910.1043.

Equivalence data enclosed have been selected from 700 points generated in 22 equivalence demonstrations. We reported that 98% of these samples were between +-25% of the VE readings in our testimony at the cotton dust hearings (Ex. 203). The enclosed data also supplement a previous submission (Ex. 235) addressing the more statistically rigorous Rockette/Wadsworth equivalence protocol.

The 100 points submitted are the most representative of process areas and range of dust levels in the 700 point base that meet all criterion given in the new protocol. We feel that data from many processing areas and different plants represent the best measure of the general applicability of the alternative method.

I will be happy to answer any questions you have regarding the equivalence information. Please send the opinion to my attention.


Arthur C. Miller, Jr.
Vice President