- Use combined stirrer/hot plates when you need both functions. The controls for the stirrer and temperature control look the same. Fires occur when the stirrer is only needed but the heat source is turned on by accident.
- Newer hot plates are manufactured to avoid sparks, older hot plates have a spark risk due to the position of the "on-off" switch on the unit itself as well as the bimetallic thermostat, which can become corroded and create a spark hazard.
- Do not heat a metal pan on a hot plate. It can damage the hot plate and even pose a shock risk.
- When removing objects from a hot plate, use tongs or thermal gloves. The same holds true when pouring hot liquids.
- Perhaps the most important thing of all is to remember to turn the hot plate off. Hot plates left on are the source of most fire related accidents.
Heating Element Safety
There are several specific pieces of laboratory equipment that warrant particular reminders when it comes to heating. These items include:
- The power switches and fan motors are not spark-free and can pose a serious ignition hazard.
- Be aware of the direction of the heat. Never direct the air flow towards one's body. Heat guns can produce up to 1100°F of flameless heat at the nozzle which can ignite clothing and can cause severe burns.
- Do not use an extension cord to power a heat gun.
- Never block the inlet grill or obstruct the air flow of the unit while in operation. If the air flow is reduced, the heat gun will overheat and potentially catch fire.
- Never leave a heat gun unattended during operation or cool-down and allow the heat gun to cool before storing it.
- Unplug the heat gun when not in use.
- As long as the layers of fiberglass cloth remain intact, the heating mantle will pose no shock hazard.
- Always use with a variable autotransformer to control the input voltage.
- Do not exceed the input voltage recommended by the mantle manufacturer. Higher voltages will cause it to overheat, melt the fiberglass insulation and expose the bare heating element.
- Heating mantles should not be used for vacuum distillation of heat sensitive or unstable materials. It's difficult to regulate precise temperature control.
- Never operate heating mantle without fluid within the flask.
- Label oil baths with the name of the oil and its maximum safe working temperature. For example, "Hot Mineral (Silicone) Oil" "Do not allow the temperature to exceed 145°C".
- Place the oil bath in secondary containment. Containment must withstand the maximum oil temperature.
- Oil expands when heated. Do not overfill bath containers.
- The temperature of oil baths must be carefully controlled so as not to exceed the flash point of the oil. Use a thermometer to monitor temperature of bath.
- Insure that water or volatile materials do not come into contact with oil baths.
- Watch for smoking of the oil. Oil that is smoking is too hot and may burst into flames. If an oil bath starts to produce smoke, turn off the heat immediately.
- Keep oil well-mixed to prevent hot spots and overheating.
- Always use hose clamps and inspect hoses for cracks or leaks. Ensure that the hose fits securely on the gas valve and the burner. Replace all hoses found to have a defect before using.
- Place the Bunsen burner away from any overhead shelving, equipment or light fixtures by at least 12 inches.
- Utilize a sparker/lighter with extended nozzle to ignite the burner. Never use a match to ignite a burner.
- Do not leave open flames unattended and never leave the laboratory while the burner is on.
- SHUT-OFF gas when done using.
- Do not use in Biological Safety Cabinets.
- Be cautious of hot surfaces when loading and unloading items. Recently dried contents inside will be extremely hot.
- Make sure to keep face, body and hands away from escaping heat when opening the door to avoid burns.
- Do not use oven to dry volatile samples. This will pose an inhalation hazard.
- To avoid explosion, glassware that has been rinsed with an organic solvent should be rinsed again with distilled water before being dried in an oven.
- Never use for human food preparation.
Accidents involving a heat source typically results in a burn, fire and/ or an explosion. Using these types of equipment in the fume hood will help protect lab personnel in the event an accident occurs. In general:
- Never use or store flammable chemicals around heating elements.
- Heating devices should be elevated to the work being performed so that heat can be removed immediately if needed.
- Never leave heating elements on while unattended.
- Inspect glassware for visible cracks, make sure glassware is heat resistant.
- The use of space heaters is prohibited in laboratories.