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.

April 26, 1990



SUBJECT: Clarification of 29 CFR 1910.1047(h)(2) Requirements for Emergency EtO Limit


This is in response to your memo of January 9, requesting an interpretation of 1910.1047 OSHA's Ethylene Oxide (EtO) standard, paragraph (h)(2). This paragraph requires:



"(2) Alerting employees. Where there is the possibility of employee exposure to EtO due to an emergency, means shall be developed to alert potentially affected employees of such occurrences promptly. Affected employees shall be immediately evacuated from the area in the event that an emergency occurs."

In the situation described in the memos you sent us, a Notification (OSHA 2-H) was issued by the Little Rock Area Office to the Veterans Administration Hospital in Fayetteville, Arkansas for a violation of 1910.1047(h)(2). The hospital utilized Enmet and AMSCO portable gas monitors during ethylene oxide sterilization runs and set the alarm to be triggered at 50 ppm. The basis for your interpretation that this did not meet the intent of the standard is the standard's excursion limit (EL) for EtO, which, at 5 ppm, is the airborne concentration of EtO to which the employer is to ensure that no employee is exposed, as averaged over a sampling period of 15 minutes.

Based on discussions with the [Directorate of Standards and Guidance], we regard the 50 ppm alarm limit utilized by the VA for their EtO monitors as an acceptable limit. There are several reasons for this. The EL is not interpreted as an emergency exposure limit, it is, instead, a PEL; the excursion limit is an allowable time-weighted average exposure under the standard as collected over a 15 minute sampling period. We assume that the 50 ppm alarm limit utilized by the VA represents an instantaneous reading and that the monitoring units you mentioned are direct reading portable gas analyzers and are capable of providing instantaneous analysis of ambient EtO levels.

It is possible that an employee's exposure could reach a peak of 50 ppm for a small amount of time and the employee's overall exposure would still be under the 8-hour PEL of 1 ppm. The intent behind the promulgation of the excursion limit was to reduce exposed employee's total EtO dose to levels below what is achievable without the EL (that is, if only the 8-hour TWA were enforced). The excursion limit is not a ceiling limit that may not be exceeded, it is a 15-minute time-weighted average exposure.

"Emergency" is defined in the EtO final standard as:

"an occurrence, such as, but not limited to, equipment failure, rupture of containers, or failure of control equipment that is likely to or does result in an unexpected significant release of EtO."



Utilizing a 50 ppm (instantaneous reading) alarm would be consistent with the intent of the provision at 1910.1047(h)(2) to alert employees of an "unexpected, significant release of EtO" that may result from an equipment failure, etc. High or peak EtO exposures can occur in regulated areas (regulated areas are defined as areas "where a reasonable expectation exists that the excursion limit would be exceeded if an employee were to work at that location all day" (see FR Vol. 53, No. 66, April 6, 1988, pg. 11433)). Therefore, setting the alarm to sound at the EL may mean that the alarm could possibly be sounding continuously, since these instruments are located near the EtO sterilizer, certainly within the regulated area(s). Again, the EL is not an emergency limit and the intent of the alarm requirement at 1910.1047(h)(2) is to warn of emergency situations (equipment or control failure) resulting in unexpected, significant releases of EtO.

Further, the 1984 EtO final standard (FR Vol. 49, No. 122, June 22, 1984) contained this same requirement at 1910.1047(h)(2). The EL for EtO had not been promulgated at that time. This fact further speaks to the intent that the requirement for EtO "alarms" not be for levels above the EL, but, again, for emergency situations as discussed above.

This interpretation is not meant to definitively state that "50 ppm" is the level at which all EtO alarms required by 1910.1047(h)(2) should be set. The standard, the preamble, and information in the rulemaking record are all silent on the establishment of a specific level for this requirement. The requirement at 1910.1047(h)(2) is performance-oriented, as it requires that "means shall be developed..." and mentions no specific level, indeed, does not specifically require an "alarm." In this situation, as in all other performance-oriented compliance requirements, it is up to the employer to meet the intent of the standard by "means" that allow him to adapt the requirements of the rule to the needs of his workplace, means that meet the intent of the standard, rather than be required to follow a specific, rigid requirement. For all of these reasons, therefore, we believe that the EtO alarm level utilized by the VA meets the intent of the standard to provide a means of alerting employees of significant releases of ethylene oxide. If you have any further questions, please feel free to contact [the Office of Health Enforcement at (202) 693-2190].



January 9, 1990



[Directorate of Enforcement Programs]
Office of Field Programs
SUBJECT: Request for Interpretation/Clarification of
29 CFR 1910.1047(h)(2)


Attached is a request from our Little Rock Area Office for an interpretation of 29 CFR 1910.1047(h)(2) with respect to what is considered to be an emergency limit for ethylene oxide. There is no concentration suggested either in the standard or in the preamble discussion.

The Veterans Administration Hospital, Fayetteville, Arkansas, has chosen to set their emergency monitor at 50 ppm. What is the suggested concentration level for setting the emergency monitors in the hospital environment described?

This request is forwarded for your response since the clarification could have nationwide implications or significance. Please furnish a copy of your response to Jerry Bailey, Assistant Regional Administrator for Technical Support.

Your assistance is appreciated.

Regional Administrator


cc: Little Rock Area Office





December 21, 1989





MEMORANDUM TO: Gilbert J. Saulter, Regional Administrator
ATTENTION: Jerry Bailey - ARA/Technical Support
SUBJECT: Standard Interpretation of 29 CFR 1910.1047(h)(2)


During a recent inspection at the Veterans Administration, 1100 North College, Fayetteville, Arkansas, the use of an Enmet Monitor set at 50 part per million for ethylene oxide was observed.

The ethylene oxide sterilizer uses a compressed gas supply cylinder of a 12:88 gas mixture (EtO:Freon). A negative pressure enclosure with local exhaust ventilation is also used in the sterilizer room. A redundant monitor is also located in the exhaust system. AMSCO portable monitors are used during sterilization and the alarm is set at 50 ppm.

The Little Rock Area Office issued a Notification (OSHA 2-H) for a violation of 29 CFR 1910.1047(h)(2). The basis of this decision is 29 CFR 1910.1047(c)(2) which states no employee shall be exposed to an airborne concentration of ethylene oxide in excess of 5 parts of ethylene oxide per million parts of air (5ppm) as averaged over a sampling period of 15 minutes.

The Veteran's Administration contends that the short term exposure limit is not an emergency limit. There is no level documented in the standard or in NIOSH documents to what constitutes an emergency. They believe having the monitors set at 50 ppm is proper.

As you can see, this same situation could occur with other hazardous chemicals at other locations. Therefore, an interpretation is needed as to the setting of a monitoring device to indicate emergency conditions versus the STEL or other exposure limits.

Your assistance in this matter will be greatly appreciated. If you have any questions please contact [the Little Rock area office at (501) 324-6291.]

PAUL J. HANSEN, Jr., Area Director

[Corrected 6/2/2005]