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 23, 1984

Mr. A. E. Burr
Vice President
Sunkiss Thermoreactors, Inc.
4900 Hickmore
Montreal, Quebec H4T 1K6 Canada

Dear Mr. Burr:

This is in response to your February 9 letter concerning the compliance of your thermoreactor product with Occupational Safety and Health Administration (OSHA) standards.

Based upon the information provided for our evaluation, it appears that your catalytic heaters may be safe to use in ovens since they received the approval of Factory Mutual Engineering Corporation (FM) for use in ovens only. The FM approval was not for the use of this equipment in spray booths where it would be subjected to overspray deposits. OSHA can make no assurance or certification that products meet our requirements. Variable workplace circumstances and the possible alteration or misapplication of an otherwise safe piece of equipment could create a hazardous condition which is beyond the control of the equipment manufacturer. Therefore, it is the policy of OSHA not to approve or endorse products.

OSHA's standards for curing apparatus are given in 29 CFR 1910.107(j) (copy enclosed). Your system does not comply with 29 CFR 1910.107(j)(2), since its wall arrangement for drying could cause a material increase in the surface temperature of the spray booth. An employer, on an individual basis, may request a variance from the existing standard if the employees are offered protection at least equivalent to that provided by the standard. The employer would need to submit to us such data as tests of the safety of the catalytic heaters when subjected to overspray, workings of the interlocks to prevent spray operations when heaters are on, length of purge cycles, amount of exhaust and makeup air required during the drying cycle, extreme temperature alarms and automatic heater shut-offs, certification of employee training, etc.

The source standard for 29 CFR 1910.107 is the NFPA 33-1969, Spray Finishing Using Flammable and Combustible Materials. The updated NFPA 33-1982 code continues to prohibit the practice of "... any arrangement which will cause a substantial increase in the surface temperature of the spray booth, room or enclosure." This is stated in paragraph 11-2 (copy enclosed), which also emphasizes the hazard of this practice in the following statement:

The susceptibility to spontaneous heating and ignition of overspray residue may be greatly increased at temperatures above normal.

The NFPA 33 Committee is aware of innovative ways of curing which provide acceptable safety to employees and is proposing to permit their use with certain restrictions as indicated in its 1984 proposed revision (copy enclosed).

You may wish to bring your concerns regarding your type of catalytic heater to the attention of the NFPA 33 Committee, which is meeting on June 6, 1984, in Boston, Massachusetts. You should contact Mr. Martin Henry, the NFPA Staff Liaison to the Committee, if you wish to attend this meeting or comment on the proposed changes. His address is:

National Fire Protection Association
Batterymarch Park
Quincy, Massachusetts 02269
Telephone: (617) 328-9290

If the NFPA 33 Committee accepts your type of equipment under specific guidelines, then OSHA could allow its use under its de minimis violation policy. Under this policy, when an employer is complying with a consensus standard such as NFPA-33 which is an updated version of a source code for an OSHA standard, OSHA regards the employer's deviation from the OSHA standard to be a de minimis violation of the Occupational Safety and Health Act, if compliance with the updated consensus code provides equivalent or better employee protection. A de minimis violation is considered to be a technical departure from a standard that does not affect employee safety and health. In such cases, no citation is issued, no penalty is proposed, and correction is not required.

Whether compliance with the updated code provides equivalent or better protection than the OSHA standard must be determined on a case-by-case basis. Our staff is happy to respond to any inquiry as to whether a specific departure from the current OSHA standard is considered to be de minimis. Finally, OSHA is attempting to update many of its standards, and it may be that in the future our regulation may be amended to reflect the changes in the latest version of NFPA-33.

I hope the above discussion and enclosures are helpful to you. Should you have any further questions, please do not hesitate to contact us.


John B. Miles, Jr., Director,
Directorate of Field Operations