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 https://www.osha.gov.

March 20, 1979

                    Regional Administrator

THRU:               DONALD E. MACKENZIE Field Coordinator

FROM:               IRVING WEISBLATT Acting Director, 
                    Federal Compliance and State Programs

SUBJECT:            Clarification of 29 CFR 1910.107 in regard to when
                    sampling for the LEL would be required

REFERENCE:          Memo of June 14, 1978, to Acting R.A. Atlanta from Bruce

Subject:            Clarification of 1910.94 & 1910.107

This memorandum, confirming several conversations between Messrs. Wendell, Brown and Barto, amplifies the discussions on 29 CFR 1910.107 in regard to when sampling for the LEL would be required. The following are examples of when or when not to sample for the LEL:

1. When organic peroxides are used in any spraying operation and documentation is available that substantiates this, 29 CFR 1910.107 stands on its own and can be cited without sampling for the LEL.

2. Inside spray booths or spray rooms where flammable and/or combustibles are used and documentation is available that would substantiate this, 29 CFR 1910.107 can be cited without sampling for the LEL.

3. Spraying areas as defined in 29 CFR 1910.107 are any areas in which dangerous quantities of flammable vapors or mists, or combustible residues, dusts, or deposits are present due to the operation of spraying processes. In spraying areas, ventilation, quantity of flammable and/or combustibles being sprayed, absence of residues, dusts or deposits, etc., make it difficult to determine if there are dangerous flammable vapors present. Therefore, sampling for the LEL would be necessary to establish that a hazard exists before citing 29 CFR 1910.107, in situations other than those found in example one and two above.