When browsing through some videos online, I recently discovered that methanol fires are invisible. That is to say, the flames are colorless and the combustion does not produce smoke. Considering the prevalence of methanol as a solvent in the world of chemistry, you’d think this tidbit of information would have come up in safety training somewhere along the line. Alas, no.

Open wheel motorsports have used neat methanol as a fuel for several decades, which means there’s plenty of video for us to observe methanol fires in action:

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While I find the idea of an invisible fire to be a safety liability, it is interesting to note that the Indy car circuit switched to neat methanol because it burns smokelessly. A wreck in the 1964 Indianapolis 500 was exacerbated by poor visibility from the thick black smoke produced during a gasoline fire. Two drivers died in the crash:

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You’d think that these racing leagues would have spiked the fuel with something that gives you an emission in the visible spectrum upon thermal excitation. Alternatively, what about coating the car and the fire suits with a bit of sodium salt for the same effect? I suppose it’s a moot point; Indy racing recently switched to ethanol as its fuel. Ethanol fires are also smokeless, but burn with a light red flame. Here’s an interesting demonstration of the combustion of various auto fuels:

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(That last video is probably a little misleading. You can’t really simulate how these fuels burn in an engine the way the guy is burning them here. I would expect all of the fuels to burn more cleanly at higher temperatures and with more oxygen.)