This article is based on a request from Frank Denny, Director of the Office of Occupational Safety and Health of the United States Department of Veterans Affairs.

During a recent conversation, Mr. Denny had indicated that two of the most frequently asked questions to personnel in his office involve matters related to the changing of ethylene oxide (EtO) cylinders, in sterile processing departments. Agency employees have complained that contradictory information is being proffered by various learned authorities.

In cooperation with the good folks at Honeywell, manufacturer of Oxyfume® sterilant gas blends, we will answer those questions.

The Questions

1.     When changing a cylinder, should I wear self-contained breathing apparatus (SCBA)?

2.     If a small leak is observed during the changing process, should I attempt to fix it, or just immediately warn everyone and evacuate the facility?

The Answers

1.     [Cylinder change/SCBA] When changing a cylinder, personal protective equipment must address these three areas:

  • Respiratory protection
  • Eye protection
  • Skin protection

In practice, respiratory and eye protection can both be achieved with a full-facepiece respirator. Any respirator used in this application must have either an end-of-service life indicator, or be a positive pressure, full-facepiece supplied air respirator.

Generally, an SCBA would not be employed routinely, but would be used in the investigation of a situation where the EtO levels are known to be high, based on some upset condition. Do not attempt to use an SCBA unless you have received proper and up-to-date training.

For skin protection, wear butyl rubber gloves. If there is any risk of a liquid spill, also wear butyl rubber boots, and a butyl rubber apron or coveralls.

2.     [Small leak protocol] In some ways, this is a loaded question, so we will have to build up to a comprehensive answer.

While rare, catastrophic leaks can occur with EtO cylinders, typically due to misadventures with the valve assembly.

ethylene oxide cylinder

For example, if the pressure relief device is removed, fast and uncontrollable release of the sterilant will occur. If this were to happen, warning of personnel and evacuation should commence at once. Presumably, such an event could only occur if the worker had confused the valve plug, which SHOULD be removed during changeover, with the pressure relief device.

The pressure relief device, which is set to 375 psig (2,586 kPa), can also activate if the cylinder is exposed to high heat. Such exposures would include:

  • Temperatures above 130 °F (54 °C)
  • Direct sunlight
  • Welding flames

As to small leaks, here are two common scenarios, and these should be handled on the spot:

a.   After removing the cylinder cap of the new (full) cylinder, it is prudent to check the valve for leaks, using a soap solution or a portable EtO analyzer. If this sort of leak is found, do not put the cylinder into service! Secure it in a well-ventilated area—away from where people are working, mark it as leaky, and contact your EtO supplier.

b.   Leaks can also occur in the connection between the sterilant supply line and the cylinder.

If you discover a leak here (using a soap solution or a portable EtO analyzer), close the valve, depressurize the sterilant supply line, and re-tighten the connection.

ethylene oxide cylinder


If the leak still cannot be stopped after connecting a second time, close the cylinder valve by turning the handwheel and depressurize the gas supply line. Follow recommended steps to disconnect the cylinder, and contact your EtO supplier. The valve may be damaged internally, or the gas supply line connection may be worn.

Note that both of these small leak scenarios can be dealt with, given proper training and suitable personal protective equipment.

Since this article is not meant to completely cover all aspects of EtO cylinder safety, it is highly recommended that you seek appropriate training from your EtO supplier. Most likely, this has already been arranged by your employer.

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