Household appliances are not designed to withstand the hazardous materials utilized in a lab nor the processes in which they are utilized.
- Household microwaves should never be used in a laboratory.
- Household hot plates should never be used in a laboratory.
Microwaves
Microwave Oven Use Hazards
Microwave ovens are used for heating and defrosting in laboratories. However, improper use of a microwave can pose a number of hazards including:
- Ignition of flammable vapors
- Electrical shock from ungrounded or faulty units
- Ignition of materials being heated
- Pressure build-up in sealed containers
- Integrity of containers holding materials
- Sudden boiling of liquid in an open container following removal
Working Safely with Microwaves
- Never attempt to heat flammable liquids or solids, hazardous substances or radioactive materials in any type of microwave oven.
- Do not place metal items inside the microwave, including aluminum foil and plastic coated magnetic stirrer bars.
- Do not modify the microwave in any way, including the removal of the grounding pin or change of the plug.
- Never use a laboratory microwave for food preparation (or kitchen microwave for laboratory materials).
- Do not heat sealed containers in a microwave. Even a loosened cap or lid poses a significant risk since microwaves can heat material so quickly that the container explodes either in the oven or shortly after removal.
- Take care to avoid overheating liquids. It is possible to raise water to a temperature greater than normal boiling point; when this occurs, any disturbance to the liquid can trigger violent boiling that could result in severe burns.
Additional Safety Measures
- Large amounts (e.g. 250 mL) of solidified agar should not be warmed in a microwave unless first chopped up with a sterile spatula. Not doing this can cause explosive vaporization in solid agar where vapor cannot escape.
- Use loose fitting sterile foam plugs or loose 'Kimwipe" plugs, rather than just relying on loosely placed cap.
- Ensure a good amount of headspace is available in the container above the material being heated.
- Set the power and timings correctly. Do not overheat.
- Thermal gloves and a face shield must be worn when removing a container from the microwave.
- Care should be taken when placing the container on the bench as not to cause unnecessary disturbance of the agar, which may cause the agar to boil over.
Microwave ovens should not be utilized as a reaction accelerator in the chemical research field. A full risk assessment must be conducted first and may only be approved in laboratory-grade equipment.
Hot Plates
Hot Plate Use Hazards
Hot plates are normally used for heating solutions to 100 C or above when steam baths cannot be used. New hot plates should be designed in a way that avoids electrical sparks and other interlock features. Hot/stirrer plates have an additional risk when operators turn on the wrong feature.
Hazards from hot plates include:
- Burn Hazard: Touching the surface of the hot plate could burn you. Caution should be taken to avoid touching the surface.
- Spark/Fire Hazard: In older hot plates, there is an electrical spark hazard from either the on-off switch or the bimetallic thermostat used to regulate temperature or both. If the equipment sparks near combustible or flammable materials, fire could result.
Working Safely with Hot Plates
- Ensure workers are trained in the safe use of all equipment prior to use.
- Always check equipment prior to use. Do not use equipment if:
- Cords are worn, frayed, or damaged. Also, do not use if the grounding pin is removed or plug is damaged.
- Sensor is corroded or damaged.
- Spark is observed.
- Do not store volatile flmamable materials near hot plate. Do not place paper or other combustible materials near hot plate.
- Limit use of older hot plate for flammables.
- Ensure the hot plate is set to the proper setting. Do not leave unattended.
Hot Plate Malfunctions Survey Info
This survey collected information from research institutions that have experienced electrical and electronic hot plate malfunctions that may or may not have resulted in equipment and facility damages.
- Read the recent survey conducted about the .