Manual of basic techniques for a health laboratory - libdoc.who.int

3. General laboratory procedures 833.5.3 Cleaning and maintenance of other laboratory equipmentCentrifuges 1Clean the bowl of the centrifuge daily or after any spillage occurs. Use 70% ethanolfor metal bowls and 1% bleach (see page 84) for plastic ones. (Do not use bleachfor metal bowls as it may cause corrosion.)Rinse the centrifuge buckets after use and remove any traces of blood, etc.Check the wiring for fraying and loose connections at regular intervals. If the centrifugeis sparking or running irregularly, the carbon brushes may need replacing.Lubrication of the centrifuge should be carried out by a specialist, according to themanufacturer’s instructions.Water-bathsIf possible fill the water-bath with distilled water or rainwater to prevent depositsforming inside. A crystal of thymol will help to prevent algal growth.Change the water and clean the inside of the water-bath at least once a month orwhenever it looks dirty. Use a thermometer to check the water temperature eachtime the water is changed as scale on the heating element may cause the thermostatto malfunction.IncubatorsIncubators are used for bacterial culture by laboratories working in microbiology.The incubator must maintain a constant average temperature of 35°C (range 33–37°C). The actual temperature must correspond to the thermostat setting whenthe instrument is used.In carbon dioxide incubators used for microbial culture, the concentration ofcarbon dioxide should be maintained at 5–10% and the humidity at 50–100%.The temperature in the incubators should be recorded daily. Like all laboratoryinstruments, incubators must be cleaned at regular intervals (at least every fortnight)and also after spillage of any material, whether infectious or non-infectious.Westergren tubesRinse in water, then leave to soak in clean water for 12 hours. Dry completely (inan incubator at 37°C, if possible). Do not use washing powder, acids or ethanol.3.5.4 DisinfectantsThere are many disinfectants that have various different chemical actions on infectiveagents. Table 3.1 lists the disinfectants that are most commonly used in healthlaboratories.CresolsCresols may be solid or liquid; they are less water-soluble than phenol, but a 5%aqueous solution can be kept as a stock solution. Cresols emulsify well in soapsolutions.LysolLysol is an emulsion of 50% cresol in an aqueous solution of soap. Cresol can bereplaced by phenol, but since phenol is a less powerful disinfectant the time of1For further information, see section 3.3.3.