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Lab Health and Safety

10 Safety Tips for Using an Oil Bath

A few years ago, a fire was started in a chemical fume hood when a researcher was attempting to heat an oil bath on a hot plate. Nobody was injured during the incident, and it was small enough to be smothered by a fire extinguisher.

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A few years ago, a fire was started in a chemical fume hood when a researcher was attempting to heat an oil bath on a hot plate. Nobody was injured during the incident, and it was small enough to be smothered by a fire extinguisher.

Apparently, the researcher had never used this hot plate and oil bath combination. Also, the person who previously used the oil bath forgot to label its contents.

When the researcher stepped away to attend to another operation, a noise coming from the hood indicated that the bath had ignited. As it turns out, the mercury thermometer being used to monitor the temperature of the bath had broken, releasing mercury into the hood.

Although the cause of the fire was never determined, there are some key safety issues that were ignored during this accident. Below you will find 10 safety tips to keep in mind while using a hot oil bath:

1. All heating oil must be labeled with the safe working temperature range before storage.

2. Avoid overheating the medium. Smoke indicates that the safe temperature range has been passed, and that the oil is highly susceptible to ignition. The main thing is not to exceed the recommended thermal limits of the fluid you're using, and be sure to discard anything that was overheated.

3. Monitor the bath closely and never leave it unattended.

4. Mix the baths well to ensure that there are no “hot spots” around the elements. Always monitor a bath's temperature using a contact thermometer or other thermal sensing devices.

5. Contain heated oil and water in a vessel that can withstand an accidental strike by a hard object.

6. Mount baths carefully on a stable horizontal support such as a laboratory jack that can be raised or lowered without danger of the bath tipping over.

7. Clamp equipment high enough above a hot bath that if the reaction begins to overheat, the bath can be lowered immediately and replaced with a cooling bath without having to readjust the equipment setup.

8. Provide secondary containment in the event of a spill as well as wear heat-resistant gloves, a fire-proof lab coat and safety glasses when handling a hot bath.

9. Take care to keep water from leaking into hot oil baths, which can cause hazardous popping and splattering.

10. Liquids expand when heated. Avoid overfilling the baths.