Many people watched as firefighters doused a tanker truck with white foam on Wednesday. The truck went up in flames after crashing into a median, in the northbound lanes of I-25, near Orchard Road.

Viewers wanted to know what the foam's story was.

South Metro truck sprays foam on tanker truck after crash (5/31/17)

Its purpose is to seal off the air, keeping it from getting to a fire. The water in the foam also helps to cool down the tank.

The truck carrying the foam is no ordinary fire truck. Crews drove it in from Centennial Airport, where its mainly used to handle aircraft fires.

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South Metro Fire has had this specific truck at the airport since 2015.

It spits out foam from the top of the truck at 750-to-1,500 gallons per minute.

South Metro truck sprays foam on tanker truck after crash (5/31/17)

The drawback though, is that once the foam reaches the oils and fuels in tanker truck like this, the mixture forms what is comparable to an ice slick. Crews then throw dirt over the oil to allow them to work. Another environmental agency will then come in to a situation like this, and clean up the foam, the fuel and the dirt, because CDOT is not a hazmat company.

Do you have a question for Next about something else to do with Wednesday's crash? Let us know by email, Facebook or with #HeyNext on Twitter.