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
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
A. CHAMBER CONSTRUCTION
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.
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.
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.
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).
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
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.
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
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
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.
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.
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
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
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.
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.
Even with a total control failure, all mechanical safety features
must be left intact.
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
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
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.
TABLE TOP AUTOCLAVES WILL NOT BE APPROVED FOR PURCHASE UNLESS
THE USER CAN DEMONSTRATE THAT THERE IS ADEQUATE VENTILATION TO ACCOMMODATE
THE RESULTING ODORS.