Does 29 CFR 1910.124(b)(1) require an employer to maintain the airborne concentration of vapors at levels below 25 percent of their lower flammable limits (LFL) within the “vapor area”?

No. A “vapor area” is defined in 29 CFR 1910.123(d) as “any space containing a dip tank, including its drain boards, associated drying or conveying equipment, and any surrounding area where the vapor concentration exceeds 25% of the LFL of the liquid in the tank.” This definition includes the vapor source, such as a dipped object, even though OSHA does not define the term “vapor source.”

While OSHA attempted to clarify the requirements associated with dipping and coating operations when it developed 1910.124, the Agency says it did not intend to create additional or more stringent obligations for employers. Thus, an employer complies with 1910.124(b)(1) when the employer limits the vapor area to the greatest extent feasible and provides ventilation sufficient to ensure that airborne concentrations of substances beyond the vapor area remain below 25 percent of the substances’ lower flammable limits. Further, by referencing NFPA 34-1995 in 1910.124(b)(4)(ii), the Agency provided additional guidance regarding the permissible scope of the vapor area in situations in which mechanical ventilation is used. Both the OSHA standard and the NFPA standard are designed to limit the size of the vapor area and to prevent dangerous vapor concentrations from migrating into areas where they may create hazards for persons working in the facility. Compliance with NFPA 34-1995 enables an employer to limit the vapor area and provide mechanical ventilation in a manner consistent with the requirements of 1910.124.