Comedian and classic car collector Jay Leno was injured on Sunday while working on one of the vehicles in his Big Dog Garage in Burbank, California.

Leno was hospitalized with burns to his face, but is expected to recover.

"I got some serious burns from a gasoline fire. I am OK. Just need a week or two to get back on my feet," Leno told Fox News Digital.

Leno's long-time mechanic George Swift told Access Hollywood that "he got sprayed with some gas" while working on one of his steam-powered cars.

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Jay Leno was working on a White steam car when he was burned. (Paul Drinkwater/NBCU Photo Bank)

Leno owns several of the archaic vehicles, including several Stanley Steamers, a 1925 Doble E-20, and a 1907 White that TMZ reported that the car involved in the incident.

But where does the gasoline come in? 

Steam engines are also known as external combustion engines, because fuel is burned outside the cylinders that drive them.

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Typically, a boiler full of water is heated by a burner, similar to how a home heating system works, but creates high pressure steam that is directed into a set of reciprocating pistons.

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The Doble's boiler is located under the car's hood. (Colin Creitz/The Enthusiast Network via Getty Images/Getty Images)

As the steam enters one end, it pushes the piston in the opposite direction, then steam is introduced into the other end to push it back.

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Steam is created as the water is heated by a burner below the tank. (Colin Creitz/The Enthusiast Network via Getty Images/Getty Images)

The engines operate smoothly and produce a lot of torque, which is why larger versions were common in industrial applications – a few of which Leno also has in his garage – but internal combustion engines eventually became more efficient, powerful and easy to operate, contributing to steam's demise in automobiles.

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The burner needs fuel to operate, of course, and while kerosene was often used because it is less volatile than gasoline, burns more cleanly than some other fuels and was usually cheaper, early Stanley Steamers were designed primarily for gasoline, and Whites and Dobles could run on either.

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Jay Leno once received a speeding ticket in a Stanley Steamer car. (Myung J. Chun/Los Angeles Times via Getty Images)

Leno was reportedly trying to unclog a fuel line when it sprayed fuel that was ignited by a spark.

Like many of his cars, Leno does not just leave the steam vehicles in his garage. He keeps them in running condition and is often seen around the Los Angeles area driving them.

And not always slowly. He was once famously caught speeding in a Stanley Steamer.

"I have the record for the oldest vehicle to be done for speeding. It was a 1912 Stanley Steamer, and I had it cranked up to 75mph on a freeway," Leno told Visor Down in 2010.

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"I'm kind of proud of that, especially considering the engine is steam-powered and makes less than 10 bhp. The cop who issued the citation was remarkably straight-faced and unimpressed with my feat, which I thought was a little unimaginative of him. How could you seriously issue a speeding ticket to something with the same engine as a small steam locomotive?"