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.

Dec. 6, 1985

Dr. George J. Reilly
Coordinator and Head, Scientific Research
Winterthur Museum & Gardens
Route 52
Winterthur, Delaware 19735

Dear Dr. Reilly:

Acting Assistant Secretary Patrick R. Tyson has asked me to respond to your letter dated November 25, requesting a permanent variance from Section 1910.242(b), Compressed air used for cleaning, of the Occupational Safety and Standards.

The enclosed copy of the OSHA Instruction STD 1-13.1 describes the intent and application of this standard. In short, the use of compressed air for cleaning purposes at pressures at or greater than 30 psi is permissible if the outlet or source is fitted with a relief device that drops the pressure to less than 30 psi if the flow is dead-ended. Appropriate personal protective equipment shall be worn as called for in the standard.

You will have to evaluate your procedures in terms of this directive. If I can be of any further assistance, please contact me at (202) 523-7193.

A variance from Section 1910.242(b) is unnecessary, therefore, no further action will be taken on your application.


James J. Concannon
Office of Variance Determination


November 25, 1985

Assistant Secretary of Labor
Washington, D.C. 20210

Dear Sir:

On the 6th of June, 1985, Mr. John A. Laird, an OSHA inspector appeared at the Winterthur Museum for an on-site inspection as the result of a complaint received in the Wilmington Office (Exhibit A). Appropriate tests were conducted with regard to the air quality of the laboratory cited (Research Building 324B) and everything was found to be satisfactory. However, during the course of the inspection, we were cited for an air hose which was in violation of OSHA-29CFR 1910.242(b) "compressed air used for cleaning purposes" which was not reduced to 30 psi or less. A citation was issued on 6/21/85 (Exhibit B). The problem was rectified and notice of our compliance was sent to Mr. J. Thomas Schrank, District Supervisor in the Wilmington Office on 7/10/85 (Exhibit C).

The purpose of this letter is to file for a permanent variance to 29 CFR 1910.242(b) for the Winterthur Museum. The Museum has an active Care of Collections Program and part of that program has been the lacquering of brass and silver objects entrusted to its care. In dealing with precious objects of art, special care must be given to the polishing of these objects prior to lacquering. The individuals involved with this task consider the procedures established by them to be a safe way to remove tarnish from an object. Commercial polishes cannot be used for the removal of tarnish from delicate art objects for they contain large amounts of abrasive material as well as tarnish inhibitors and other chemicals such as ammonia which can cause further degradation of the object if not completely removed. The Museum has chosen to use only a fine abrasive called whiting (calcium carbonate) which is made into a slurry by mixing with limited amounts of reagent alcohol (denatured ethyl alcohol) for the polishing of its precious metal works of art.

When an object is polished in Room 324B of the Research Building (Photo 1) small amounts of abrasive residue are trapped in the crevices of the object (Photo 2). All of the polish residue must be removed from the object prior to lacquering and this is done by blowing compressed air over the object (Photos 3 & 4). All of the polish residue is removed from the object by this procedure (Photo 5), thereby rendering the surface suitable for lacquering.

As the result of the citation, the compressed air supply has been fitted with a Milton Safety Blow Gun #131 which is in compliance with 29 CFR 1910.242(b). However, there is insufficient pressure to remove the polishresidue that is trapped in the crevices of the object as the result of the polishing process (Photo 6). While it is sometimes possible to brush the residue from brass or bronze objects, this method cannot be applied to silver objects. Silver is soft in comparison to brass and bronze, and if a brush which is stiff enough to remove the residue is used, scratching of the surface of the object results. Consequently, compressed air with sufficient pressure to remove the residue is the only way to completely remove the residue from the surface of the object.

The compressed air line also serves another very important function in that it is used to dry the object. Metal holloware pieces are often intricate in design with many nooks and crannies that can hold liquid cleaning solutions. These areas often cannot be reached by anything other than compressed air. If the object is not thoroughly dried inside and out, such solutions can escape at a later time after the object has been placed back in the Museum and thereby severely damage other objects such as tables, carpets, floors, etc. in the Museum.

The bottom line is that we need to have a compressed air source with a nozzle pressure in excess of the 30 psi limit imposed by OSHA. The photographs clearly demonstrate that every precaution is being taken to insure the safety of the technician(s) carrying out the process as is illustrated by the fact that gloves are worn as part of the cleaning procedure. The Museum feels that it has explored every alternative to work within the confines of 29 CFR 1910.242(b) and has not found an acceptable alternative. Therefore, the Museum wishes to be granted a permanent variance to 29 CFR 1910.242(b) for the purpose of cleaning and preparing works of art for our lacquering program.

If you have any questions, please feel free to contact the Museum for further discussion.

Sincerely yours,

George J. Reilly
Coordinator and Head, Scientific Research
Winterthur Museum & Gardens


Complaint Number 70578315

Winterthur Museum
Winterthur, DE 19735

Management Official - Nancy Richards, Curator

Museum, Antiques


Inadequate ventilation for workers using solvents (acetone, xylene, petroleum benzine, lacquer thinner) and aluminum oxide in lab 324B of Research Bldg. Two workers work here cleaning and lacquering metal objects. Two elephant trunks and a hood are available but still not enough.