Archive Notice - OSHA Archive

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November 4, 1976

OSHA/Technical Support

Clarification Paint Spray Booth & Spray Areas

All Area Directors

There appears to be some confusion as to the application of 1910.94, 1910.107 and 1910.308 and 309 to paint spray operations. An attempt is being made to clarify the requirements outlined in the standards and their source documents.

The definitions used in the standards must be clearly defined and understood by all personnel. Therefore, the first element of this discussion must relate to definitions and their meaning as interpretated from the above referenced material.

1910.94(c)(1)(iii): Spray Room: A spray room is a room in which spray-finishing operations not conducted in a spray booth are performed separately from other areas. The same definition appears in ANSI Z9.3, 1964, paragraph 2.3, which is the source document for the standard. Neither 1910.107 or the NFPA Code define a spray room.

1910.94(c)(1)(ii): Spray Booth: This paragraph refers to the definition contained in 1910.107(a). 1910.107(a)(3) defines a spray booth as; a power-ventilated structure provided to enclose or accommodate a spraying operation to confine and limit the escape of spray, vapor, and residue, and to safely conduct or direct them to an exhaust system. ANSI Z9.3, 1964, paragraph 2.2, refers to paragraph 103 of Appendix A, which is identical to the above. NFPA 33, Chapter 1, paragraph 105, also contains an identical definition. In addition, each of the above references contain definitions of specific types of spray booths which have specific features.

In any discussion of spray booths the physical size of the booth becomes of prime importance since the size of the booth may range from something which will accommodate a product 1 inch in length by 1 inch in width by 1 inch in height to a booth which will accommodate an object 20 feet in width by 25 feet in height and 100 feet in length. Obviously, the requirements of each of these booths would be radically different in relation to personal protective equipment and ventilation.

From the definitions provided and the wide range of spray booth size, it seems rather obvious that a spray booth and a spray room could be treated as same under certain conditions; for example, in most cases where the employee could enter the face of the booth.

1910.107(a)(2): Spray Area: Any area in which dangerous quantities of flammable vapors or mists, or combustible residues, dusts, or deposits are present due to the operation of spraying processes. NFPA 33, Chapter 1, paragraph 104 and ANSI Z9.3, Appendix A, paragraph 102, contain additional information which describes conditions which constitute a spray area.

The key words in these definitions are "dangerous quantities of" a substance. Therefore, to establish that a dangerous quantity exists, sampling must be accomplished to establish that the concentration is in-fact-above the lower explosive limit (LEL). It should also be noted that neither of these standards address the toxicity of any material. Toxicity is addressed only under 1910.1000, and also requires sampling to establish the concentration is in fact above the time weighted average for the substance.

In summary, adequate sampling in accordance with recognized methods are essential in sustaining the violation by establishing that a hazard did in fact exist due to documented evidence that the toxic limits of the material were exceeded or that the concentrations were above 25 percent of the lower explosive limits were exceeded.

Even though table G10 of 1910.94(c)(6)(i) establishes velocity ranges for various operations in a spray booth, there is still a requirement to establish that the hazard did exist. Therefore, simple velocity measurements are inadequate. 1910.94(c)(6)(ii) establishes a requirement that the vapor concentration in the booth be kept below 25 percent of the lower explosive limit. Therefore, if the concentrations are kept below 25 percent of the lower explosive limit in all areas of the booth, even though the air velocities in the cross sectional area of the booth are below that defined by table G10, 1910.94(c)(6)(ii), it is doubtful that a citation could be legally sustained. On the other hand if concentrations exceed either of the referenced levels, we would cite regardless of air flow.

It should also be pointed out that these velocities as outlined in table G10 of 1910.94 were originally designed to reduce the concentrations of toxic or flammable vapor below the threshold limit valve or the lower explosive limit and that simple velocity measurement would assure that the exposure of an employee was within the limits of tolerance except in the most unusual circumstances.

Since the standards were developed with a built-in safety factor to protect the employee, it would seem that if the flow velocities were measured at or above the valves required by the standard that one could assume that a hazard did not exist. It would appear that we are applying a double standard to the operation of which only one is necessary except in very unusual circumstances, but we must establish that a hazard was present and therefore, the requirement for sampling.

Since we have defined a spray area in 1910.107(a)(2) - as where dangerous quantities of vapor or mist, etc. are present - it is not entirely compatible with the definition of a hazardous area as defined in NFPA Electric Code, Article 516. This definition (NFPA, Article 516) does not rely on concentrations, but makes a determination on the basis of use of a flammable or combustible substance. In view of the definition contained in NFPA Electric Code, Article 516, the electric wiring in all spraying areas (Spray booths, rooms, etc.) where spray finishing is performed regularly or frequently shall conform to the wiring requirements of the Code. The question then arises as to what is regular or frequently and what quantities are involved.

If a spray finish operation is a part of a daily production schedule, it is considered to be performed regularly. If it is not part of a daily production schedule but is performed on multiple shifts or days during a week then it is frequent.

Operations involving small quantities of spray materials used in areas where the quantity of flammable material would not produce a concentration in excess of 25 percent of the lower explosive limit should not be considered as spray areas as related to ventilation or the National Electric Code, unless there is documentation that the lower explosive limit has been exceeded in areas outside of the direct spray area.

Cois M. Brown
Originator: Carlyle F. Bunn
Assistant Regional Administrator
Safety Engineer for Technical Support