Under Pressure? Keeping the Heat on Your Autoclave
by Christopher Aston
Autoclaves are programmable pressurized steam chambers that serve two purposes in research laboratories: to sterilize reagents or equipment and to decontaminate infectious waste. The ability of these laboratory work horses to perform such tasks effectively and consistently is often taken for granted. The consequences of not paying attention to the quality control needs of your autoclave are that product sterility may not be accomplished, or the more dangerous scenario in which pathogens are not killed, with the resulting waste potentially posing a risk to those that handle it.
The proper combination of high pressure, steam and time is critical to the successful sterilization of an autoclave load. A number of verifications methods are available to ensure that your autoclave cycle has reached sufficient temperature and pressure, for a long enough period, to sterilize. The most common, autoclave tape, is easy to use, but not a fail-safe indicator of sterilization. When attached to glassware or a waste bag, hash-marks or indicators on the white tape blacken after only brief exposure to a temperature of 121°C, a potential false-positive. For greater accuracy, when the autoclave is used for sterilizing infectious waste, performance should be periodically validated by using Geobacillus stearothermophilus spore vials. Place a vial in a hard-to-reach area of a mock challenge load and attach a string to facilitate removal after autoclaving. Incubate as directed; a lack of turbidity indicates that the autoclave is achieving sterilizing conditions.
A maximum-registering thermometer, also placed in a challenging area, will indicate the highest temperate the autoclave reached, but these provide only a snapshot and they contain mercury, which presents its own environmental concerns. Better still, a data logger is an electronic thermometer that records temperatures temporally and can download data to a computer. Users are often surprised to realize that heat and steam have not reached the center of a large load, but the remedy is usually to extend the cycle length and/or distribute the load into smaller bags to enable more steam to circulate. If extending the cycle length and load distribution do not produce the desired results, a service engineer should be contacted immediately to diagnose the autoclave.
Laser Safety by Occupational Safety Team
Research involving lasers often involves manipulation of an exposed beam through a maze of optical elements. The primary hazards of lasers used in research are the highly-focused, energy-dense beams of monochromatic light and the high voltages needed to operate such equipment. Permanent injury can result from exposure to laser light, so users must be properly trained in the safe use of such equipment.
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