The most preferred method of sterilizing laboratory equipment and tools is an autoclave. Basic autoclaving apparatus, much similar to a pressure cooker, use a combination of heat, pressure, and steam to sterilize lab materials made of both glass and plastic. Steam heat kills bacteria, germs and other spores which are simply resistant to boiling water and soap. Thus, autoclaving is the most effective way of controlling microbial levels for laboratory apparatus like containers, bottle caps, and medical instruments.
Material selection – Glass/Plastic
Regarding plastic Science Equipment, not all plastics are fit to be autoclaved. Products composed of fluoropolymers like Teflon, FEP and ETFE, polypropylene and its copolymers are safe for repeated autoclaving while polycarbonate materials might break down after multiple cycles. Separate gas sterilization using Ethylene oxide formaldehyde is required for resins like PET, PETG, LDPE, and HDPE.
Glass, which is generally considered safe for autoclaving, should be sterilized with certain precautions. For instance, when lab glassware bottles are sterilized along with their caps, bottle explosion can be prevented by loosening the caps. Another common practice is to place an aluminium foil with autoclave tape inside the bottle to keep it sterile. The tape turns black which also works as an indicator that the bottle is sterilized. As compared to all other glassware, borosilicate withstands the highest autoclaving stress.
With regard to closure liners, Rubber and Teflon liners are the only recommended living materials that are safe for autoclaving.
Guidelines for autoclaving
While every Lab follows its own set of autoclaving guidelines, the following recommended steps must be kept in mind.
Preparation of autoclave and materials: All Science Equipment that needs to go in the autoclave should be washed with distilled water beforehand. Only materials that are safe and can withstand autoclave steam and heat pressure should be selected. If necessary, stainless steel or polypropylene tubs should be used as separate containments with enough space for steam circulation.
Sealing: Although autoclaves lock automatically, manual locks must be safely secured to prevent accidental leakage.
Selection of cycle and start: The recommended cycle should be chosen as per goods, for instance, liquid or slow exhaust cycle is for dry equipment like lab glassware. The specific sterilization and drying time should be set and start pressed.
End Safety: Using protective gloves, allowing items to cool before touching and letting pressure return to zero before opening are essential safety measures to prevent accidents.