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.

July 13, 1994

Kenneth A. Krukonis
Technical Manager
Fox River Paper Company
Rising Paper Division
Housatonic, Massachusetts 01236

Dear Mr. Krukonis:

This is in response to your letter of August 31, which you wrote to Mr. Ronald E. Morin of the Occupational Safety and Health Administration's (OSHA) Springfield Area Office, requesting an interpretation of the "order of testing" requirement in 29 CFR 1910.146(d)(5)(ii) and 29 CFR 1910.146(d)(5)(iii). Your letter has been forwarded to this Office for reply. Please accept our apology for the delay in this response.

You state in your letter that your permit spaces do not contain flammable gas and yet you are sampling for hydrogen sulfide which is flammable between the range of 4.3% to 46% concentration. Where there is no potential for a flammable atmosphere hazard, you are correct in proceeding to monitor for potential toxic air contaminants. If hydrogen sulfide is the only toxic potentially present in the permit spaces, OSHA will consider the proper use of the MSA #361 analyzer to comply with 29 CFR 1910.146(c)(5)(ii)(C) and 29 CFR 1910.146(d)(5)(iii).

In addition, given the automatic sampling program feature of the instrument described in your letter, OSHA believes that deviation from the sequence of testing mandated by the referenced standards will not have significant impact on employee safety and health at the Rising Paper Division of the Fox River Paper Company. The rapidity of readout of your instrument and the fact that it continuously cycles (every 5 seconds) obviates the fixed sequence of testing called for in the standard. Prudent practice dictates that specific values of each substance being recorded would be the average of several cycles.

We hope this information will be helpful. Please feel free to contact us if we can provide any further information or assistance regarding this matter.


John B. Miles, Director
Directorate of Compliance Programs

September 16, 1993

                       Directorate at Compliance Programs

THROUGH:                LEO CAREY, Director
                       Office of Field Programs

FROM:                   JOHN B. MILES, JR.
                       Regional Administrator

SUBJECT:                Multigas Alarm Used in Confined Spaces

The attached letter from Kenneth Krukonis at Fox River Paper Co., was forwarded to us recently by our Springfield Area Office. Since the multigas alarm, which is the subject of the letter, is distributed by a national company, it is more appropriate that your office provide the response to the letter. A copy of our interim response is also attached.


August 31, 1993

Mr. Ronald E. Morin
U.S. Department of Labor
Occupational Safety & Health Administration
1145 Main Street, Room 108
Springfield, Massachusetts 01103

Subject: Request for Interpretation/Clarification 29CFR 1910.146 "Permit Required Confined Spaces"

Dear Mr. Morin:

     Reference:        29CFR 1910.146(c)(5)(ii)(C) p. 4551
                         29CFR 1910.146(d)(5)(iii) p. 4552
                                          Federal Register
                                            Vol. 58, No. 9
                                    dated January 14, 1993

Both references pertain to air quality testing before entering a confined space. In each case the Order of Testing is specifically stated to be:

1. Oxygen
2. Flammable Gases and Vapors
3. Toxic Gases

To test the atmosphere in our confined spaces, Rising Paper Company uses the MSA (Mine Safety Appliances Company) Model #361 Hydrogen Sulfide, Combustible Gas and Oxygen Alarm. These are reliable, accurate, and expensive, air quality analyzers. These instruments have an automatic sampling program which samples the air at five (5) second intervals for:

1. Oxygen
2. Hydrogen Sulfide
3. Flammable Gases and Vapors

This order of testing cannot be changed by the instrument operator.

It appears that oxygen is the critical test which must be performed first since most combustible gas meters are oxygen dependent. See: Summary and explanation of Permit Required Confined Spaces 29CFR 1910.146, page 27, OSHA Office of Training and Education, February 1993.

The rationale between what should be tested second and third does not appear applicable in our case since our confined spaces do not contain flammable gas, and we cannot change the sampling/testing sequence of our instruments. It appears to us that the writer of the standard may have assumed individual testing instruments rather than an integrated unit.

It is our intention to continue testing with our present equipment while we wait for clarification.


Kenneth A. Krukonis
Technical Manager