Effective February 1, 1997, sterilizer purchases must be approved by the Biosafety Officer. A variety of factors must be taken into consideration prior to purchasing an autoclave. The selection of an autoclave must not be solely based on the purchase price. This guide has been designed to help you in making an educated decision in purchasing your sterilizer.


Before you purchase an autoclave, you must understand what the factors in which the principle of steam sterilization is based on:

  • length of time in the cycle
  • temperature
  • contact
  • pressure
  • steam



  1. Nickel clad chambers are required: Chlorides are often used in laboratory medias and solutions. Chlorides are known to cause corrosion and pitting of stainless steel that will eventually lead to possible stress cracking of the chamber. Chamber failure may result, posing a potential safety problem.
  2. The chamber weldments, doors and jacket shall be designed to meet the requirements and so be stamped by ASME. This will ensure that the requirements of the ASME Boiler and Pressure Vessel Code, Section IX. are met.
  3. A welded endring of Monel or similar material of strength and corrosion resistance shall make up the door frame. This will ensure that there will be adequate protection against stress corrosion that can weaken the design integrity resulting in a door failure and safety hazard.


  1. A microcomputer control system is preferred.

    Electromechanical controls are not recommended because they cannot maintain the required documentation and control needed for GLP (Good Laboratory Practice).

  2. The control should be mounted so as not to expose the sensitive components to steam and heat.

    Controls mounted over the door are not acceptable. This will extend the usable life of the controls and minimize malfunctions. The control must document all cycle information, including key transition points in the cycle, alarms and deviations that may jeopardize the sterilization process, resulting in inadequate decontamination.

  3. All information and alarms should be in COMPLETE MESSAGES.

    Coded information that requires a separate manual or chart to decipher what is on the screen or printout. An operator must respond to an emergency as quickly as possible.

  4. Controls must document the following minimum cycle alarms:
    • Vessel Flood Alarm

      This alarm informs the operator that steam supply failure causes a vessel flood condition. A flooded chamber filled with hot water could result in a serious burn to the operator if he should open the door unaware of the problem.

    • Steam Table Deviation Alarm

      This alarm informs the operator that the chamber pressure does not meet the saturated steam table values within 5 psi. This is important to guarantee quality control and assure the operator of a proper steam sterilization process.

    • Chamber Drain Probe Alarm

      This alarm informs the operator that the chamber drain probe has failed. This will ensure that the operation is aware of this problem and that corrective maintenance can be arranged.

    • Under Temperature Alarm

      This alarm informs the operator that the temperature has dropped below a set temperature required for adequate sterilization.

    • Over Temperature Alarm

      This alarm informs the operator that the temperature has gone above a set point. This is important with heat labile medias that can be destroyed if sterilized at too high a temperature.

  5. The sterilizer must provide a manual control that can run a complete cycle, from start to finish manually, in the event of a power failure.

    Failure to complete a cycle may result in injury to the operator if partially sterilized material must be removed forcibly from the chamber to reset the sterilizer. At a minimum, the operator will be inconvenienced having to restart the sterilization cycle.

  6. The manual control must be located in an easily accessible and safe location for usage, not behind the unit or in an area that is hard to get at.

    This feature is critical in emergency situations because it allows the complete operation of a cycle with no electrical power. It should also allow manual exhausting of the sterilizer chamber during a malfunction that would otherwise trap a load in the chamber.

  7. The sterilizer should also provide a tamper proof control with an access code that will prevent programming changes of the cycle parameters (time, temperature) with one or all of the programmed cycles.

    This feature is important to insure proper sterilization of Bio-hazard decontamination and documentation that is required for the load. No "short cuts" can be taken to reduce time, creating an improperly sterilized load

  8. The tamper proof control feature must only lock out changes to the cycle parameters, and not the operation of the sterilizer.

    The tamper proof control feature must not interfere with the function of the sterilizer. Furthermore, a key lock is not satisfactory due to the fact that misplacement or loss of the key may also shut down the unit.


  1. The autoclave door should be designed with several independent mechanical and control features that provide for safety.

    a. A control lock-out switch in the door that prevents starting a cycle if the door is not closed and locked.

    b. Mechanical steam pressure lock - chamber pressure should "activate" a mechanism engaging the lock mechanism. This will prevent an operator from opening a door if pressure exists in the chamber.

    c. Visual chamber gauge that easily identifies pressure in the chamber must be accessible to the operator. This gauge is a back-up to the control read out and will operate with no electrical power to the unit.

  2. Even with a total control failure, all mechanical safety features must be left intact.


  1. The sterilizer should be supported on a steel stand, appropriately coated for corrosion protection.

    The stand must be designed to meet Seismic, Title 24 (Division T-17 of part 6) Zone 4, California Administrative Code.


Questions to ask your autoclave vendor:

A. What is the cost of maintenance per year of operation?

Be sure you compare the costs of replacement parts and the years of warranty because the purchase price will not factor future repair costs in.

B. What is the warranty of the autoclave?

Some autoclave companies charge a lower purchase price but offer a shorter warranty. If a warranty is important to you, ensure that you compare warranties and maintenance service contracts before purchasing. Any savings on the purchase price may disappear after compare the cost of maintenance.

C. What is the cost of installation?

Be sure that if you order a sterilizer that you will not have to spend an exorbant amount to install it. Plumbing and room exhaust renovations may be prohibitively expensive.

D. Does the company have a service representative in the area?

Some autoclaves are foreign made and therefore, service representatives are often not available. Be sure that you can get information and a service representative when you need one.


Lab design is very important. The room must have adequate plumbing and electricity. Each autoclave must be installed with a canopy exhaust or other suitable means to dissipate the heat and odors which may be generated during the sterilization process.