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Too Hot to Handle

A 3-Step Program for Working with Autoclaves

Vince McLeod, CIH

Vince McLeod is an American Board of Industrial Hygiene-certified industrial hygienist and the senior industrial hygienist with Ascend Environmental + Health Hygiene LLC in Winter Garden, Florida. He has more...

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Like the coffee pot used for brewing your favorite morning beverage, an autoclave is such a common and familiar piece of lab equipment that it is easy to overlook the associated hazards. If we do not think about what might go wrong, sooner or later we will get burned (couldn’t resist the bad pun). So the Safety Guys thought it would be a fine time to discuss one of our hot topics (OK, OK, no more). Seriously, by following our simple three-step program of training, testing/monitoring/maintenance, and record keeping, you can avoid mishaps and potential significant damage or injury.

Caution: Hot SurfaceRecognizing the hazards

Just consider autoclaves large, specialized pressure cookers. Autoclaves use heat and pressure with water to create superheated steam. Accordingly, they can pose significant hazards to untrained or lackadaisical employees.

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Autoclaves are usually needed for two basic purposes, either to steam-sterilize media, instruments, or lab equipment such as glassware and specialized implements or to inactivate biological waste materials.1 The main hazards are physical ones presented by high temperatures, steam, and pressure. Effective sterilization requires steam temperatures in excess of 250°F (121°C). Typical autoclave pressurization is at least 20 pounds per square inch (psi). Depending on the use, additional biological hazards such as infectious materials or physical hazards from sharps may be of concern. By utilizing the practical information and guidance given here (as well as from many other sources online), researchers are ensured safe operation of autoclaves in the laboratory.

Training, the first step

Even though loading and running an autoclave may seem as simple as using your dishwasher at home, some forethought is required to operate the autoclave safely and efficiently. Begin by becoming thoroughly familiar with the owner/operator’s manual for your particular machine. Controls vary between brands, and each has its own unique loading characteristics, load-sizing requirements, cycle settings, and cycle types.2 The amount and type of each material requiring sterilization or inactivation/decontamination will determine the cycle needed. It is highly recommended that the manufacturer’s operation manual be copied (perhaps even water-proofed/laminated) and a copy be kept in the room with the autoclave.

Instill a policy whereby all users are trained prior to operating any autoclave. Principal investigators or laboratory supervisors should bear the responsibility of ensuring this is done. Document all training, and maintain copies of the records in the lab.

At a minimum, training should cover:

• Location, function, and use of controls

• Proper loading and unloading (including packaging, sizing, and testing protocols)

• Required personal protective equipment (heat-resistant gloves, lab coats, eye protection, and closed-toed shoes)

• Incident and maintenance reporting; record keeping

• Emergency procedures

Step Two - monitoring and testing autoclave effectiveness

In order to make sure our autoclave is functioning properly and sterilization/inactivation is effective, we need to monitor the operation of the autoclave and routinely test sterilization cycles. In fact, in Florida this is mandated by a Florida Administrative Code for handling biomedical wastes, FAC 64E-1.1 Under this law autoclaves must be tested before being placed into service and periodically afterward. For autoclaves used to inactivate human pathogens, blood, tissues, clinical samples, etc., testing is required every 40 hours of use. Autoclaves used to sterilize other materials must be tested every six months. This is a reasonable testing schedule for most research laboratories. Other institutions recommend testing at least once per month with biological indicators.2

Testing an autoclave’s sterilization effectiveness requires the use of biological indicators. These are available in commercially prepared test kits containing bacterial spores—usually Bacillus stearothermophilus (e.g., Prospore2™). Most spore vial test kits require incubation of the autoclaved test vial along with a nonautoclaved control vial. Incubation will allow surviving spores to grow. It is recommended that test loads (if used) approximate the weight and density of actual waste or materials normally autoclaved. For best results, test vials should be placed at the bottom, top, front, rear, and center of the autoclave chamber, by placing vials in those positions of the test load or making a number of smaller test packs with vials in the center and placing the packs appropriately in the chamber. In this way, the correct parameters for sterilization (time, temperature, and pressure) can be determined.

Third and final step - record keeping

A good autoclave safety program must include documentation. Principal investigators and supervisors are responsible for ensuring proper records are kept up to date. Autoclave users should be responsible for recording autoclave run information.

We have already mentioned keeping training records. In addition, we recommend keeping records of all onsite maintenance performed. Only contractors approved by the manufacturer should perform maintenance. Keep contact information posted conveniently.

Each load processed in the autoclave should be logged. Record the date, time, and operator’s name and contact information (e.g., lab, room number, and phone number). Indicate whether the load is biohazardous material or not, and record the temperature, pressure, and time length for the cycle. If the autoclave data can be printed out or is recorded on a cycle wheel, save the printout or disk.

Finally, include in the log sheet information for all efficiency tests performed and the results of each test.

Summing up

Additional information and technical assistance is available from manufacturers as well as the NIOSH, OSHA, and many academic websites. The key to working with autoclaves is first to recognize the hazards, followed by training, testing, and record keeping. In the areas where autoclaves are used, it is most important to ensure proper and sufficient facility supply and exhaust ventilation as well as use of appropriate personal protective equipment. By using a little forethought and planning, you can avoid being placed in the hot seat.


1. Safe and Effective Use of Autoclaves. Environment, Health and Safety Fact Sheet #33. University of California, Berkeley. 2011. ehs/pubs/33autoclv.pdf

2. Environmental Health and Safety Update — Autoclave Safety. Environmental Health and Safety. Weill Cornell Medical College. 2003. static_local/pdfs/autoclave_safety.pdf

3. Biomedical Waste Program, Florida Department of Health, Bureau of   Environmental Health. 2002. http://www.