Sparking : In ordinary domestic situations, small electrical sparks are usually not hazardous. In certain conditions which are frequently encountered in science labs, even the smallest sparks can produce catastrophic results due to the presence of dust or flammable fumes and vapours. At the very least, sparks will interfere with electronic equipment such as pH meters. Typical sources of sparking in the lab are:

i) dirty switches

ii) bimetallic thermostats

iii) static sources (see above)

iv) live sockets

You can find examples of equipment designed specially to overcome the problems of sparking in refrigerators or petroleum stores. Domestic refrigerators are not spark-proof and must not be used in the lab.