The New AAMI Chemical Sterilization and High Level Disinfection Standard

As mentioned earlier in this blog, AAMI recently released a revised version of ST58, "Chemical sterilization and high-level disinfection in health care facilities" and copies are available from the AAMI website. Most people in healthcare know of AAMI and the AAMI standards which provide best practices for a range of healthcare operations. AAMI has several standards associated with sterilization and high level disinfection/disinfectant (HLD) and these standards have become the go-to documents for current best practices. Sterilization and HLD is a subject currently undergoing rapid developments with new equipment, new chemicals and new practices introduced in recent years and this topic is likely to continue to rapidly evolve.

The completely revised ST58 standard covers both gas sterilization (hydrogen peroxide and ozone) as well as HLDs (glutaraldehyde, o-phthalaldehdye (OPA), peracetic acid (PAA) and sodium hypochlorite (NaOCl)) and provides practical advice to enable users to employ the best practices. Ethylene oxide (EtO) is not included in ST58 since it has its own standard ST41
Ethylene oxide sterilization in health care facilities: Safety and effectiveness.

Compared to the prior version, this new version has greater emphasis on workplace safety, a subject about which ChemDAQ cares passionately about, well beyond gas detection. ChemDAQ's own David Hilliker and Richard Warburton served on the AAMI Chemical Sterilants Hospital Practice Working Group that revised the standard.

About half of the standard is comprised of annexes and each of the FDA approved chemical sterilants and HLDs has its own annex that provides succinct information including the following topics:

• Sterilant/ HLD chemical's properties and how it is used
• Health effects (short and long term)
• Exposure limits
• Suitable personal protective equipment for eyes, skin, respiratory system
• Guidance on how to use the chemical safety (ventilation, transportation, storing, use, rinsing (for HLDs))
• What to do in the event of a leaks or spill
• Disposal and 
• Vapor monitoring. 

Hydrogen peroxide is listed twice, once in Annex C as an HLD and again in Annex H as a sterilant gas (Steris' VHP & ASP's plasma sterilizers) since the applications are very different.

The vapor monitoring section in each annex has been updated to indicate the need for continuous gas monitoring and whether they are commercially available. For example, in light of the hazards of inhaling hydrogen peroxide vapor, the vapor monitoring section of annex H now reads:

H.7 Vapor monitoring
Vapor monitoring is recommended if there is the potential for the hydrogen peroxide vapor concentration to exceed the OSHA recommended permissible exposure limits. Emissions from properly operated and maintained chemical vapor sterilizers should be well below the OSHA PEL (see H.4.1.3), but sterilizers and exhaust systems, as with any other complex equipment, can and sometimes do fail. If monitoring is deemed necessary, continuous personal and area monitors for hydrogen peroxide are commercially available.

Gas and vapor emissions can occur from even the best made equipment and odor is an unreliable indicator of the presence and concentration of hydrogen peroxide gas below hazardous concentrations. Continuous gas monitoring systems are available to help employers satisfy the requirement to provide a safe work environment by providing alerts in case of potentially hazardous concentrations, informing workers when it is safe to return after a release and provide record keeping. Review the SDS and consult the suppliers of the hydrogen peroxide solutions and the manufacturers of the sterilizer and the gas monitoring equipment for more information.

In addition to the chemical annexes, there is also a new section (Annex N) that provides users some background on gas monitoring, the pros and cons of the technologies available and the difference between personal monitoring and area monitoring and the advantages of each. This annex should prove very valuable to anyone who uses chemical sterilization and who knows they need gas monitoring but is not sure where to start. 

Of course, readers of this blog know that the best place to start for any gas/vapor monitoring question is www.chemdaq.com. ChemDAQ offers continuous gas monitors for ethylene oxide, hydrogen peroxide, peracetic acid and ozone among others.


While the annexes are chemical specific, there is a lot of valuable general information in the body of the annexes, especially regarding:

• The safe use of chemical sterilants and HLDs 
• Location of a sterilizer or automatic reprocessor
• Storage of chemicals
• Qualifications and training of personnel
• Personal protective equipment
• Selection of appropriate sterilization technologies including health and safety considerations, 
• Decontamination
• Device storage
• Quality control and Quality improvement.

 The new ST58 standard should prove to be a valuable resource to those healthcare facilities that use chemical sterilization and high level disinfection.