Flammable solvents and hot oil was always a combination that honestly scared me, but that was how I had been taught to perform reactions. As a keen cook, I knew never to put a hot pan of oil near water, yet in my former life as a chemist, that is precisely what I did in the lab day after day.

There were so many risks and fire hazards were just part of my everyday life in the lab—I honestly wish I could have known “current me” back then! There are many alternatives that can make scientists’ working lives so much safer without negatively impacting their chemistry.

Hot Oil + Flammable Solvents: The Risk

Having a dish full of oil is an inherent safety hazard, and in a busy fume hood, solvents are never far away, nor is a heating source. Together, they are an unpleasant and potentially dangerous combination. Over time and multiple heating/cooling cycles, oil degrades too, reducing its flash point. If heated excessively, oil can spit, and in the worst case, ignite.

There have been many cases that demonstrate what can happen when oil baths go wrong:

Thankfully, these days, universities have to offer specific guidance for those using oil baths. Here are just a couple of examples of this kind of advice:

Hot Oil + Flammable Solvents: A Safer Alternative

Most chemical reactions need some heat to take place, but it never occurred to me that there was already enough risk involved in just handling these chemicals, and that a method existed where I didn’t have to add the extra risk factor of combining heating and oil too.

Heating blocks have been designed specifically to replace oil baths, swapping out oil with aluminum blocks as a method of incredibly effective heat-transfer. Aluminum blocks don’t degrade and can offer the same or better heating performance and uniformity. Using aluminum blocks also removes the risk of being splashed by hot oil, or hot oil starting a fire in your lab. Very importantly, your work need never be contaminated by that oil again.

(Download Asynt’s best practice guide for the safe use of laboratory heating blocks here. It’s free, and no registration required.)

Cold Water + Hot Oil: The Risk

Some reactions I carried out as a chemist involved reflux (boiling a solvent so that it turns to gas) and using a water condenser to cool the solvent back down to liquid, thereby preventing it from escaping and the reaction “boiling dry.”

But what if the water condenser above the reaction leaks? This often happens with variable water pressure and loose tubing connections to a tap. Without even considering what might be inside the flask, a water condenser can present many risks. What if it drips into hot oil?

Cold Water + Hot Oil: A Safer Alternative

With a waterless reflux condenser, water does not drip, effectively removing another fire hazard from your lab. Waterless condensers help the environment too. Besides saving innocent tap water from going straight down the drain (at a constant rate of approximately two liters per minute for potentially days on end), a waterless system will avert floods, which can be hazardous to the environment, your health, and your budget.

Flood-Related Resources:


Arran SolomonszABOUT THE AUTHOR: In his former life as a chemist, Dr. Arran Solomonsz was hands-on at his fume hood for 95% of the day, with the remainder of the time spent populating the essential Control of Substances Hazardous to Health (COSHH) risk assessments.

Today, he’s on the other side of the fume hood at Asynt, a UK-based company created by chemists and for chemists, specializing in “clean, green, and safe lab equipment, with no compromise on quality or effectiveness.”