Blown Away by an Air Compressor

Okay, I just wanted to write about this really cool little piece of tech magic I witnessed today. So I just went to Discount Tire to put some air in my tires. I happen to know for a fact that my tires are rated for exactly 42 PSI. At Discount Tire they have this little device that scans the tag in the door sill to read the car’s recommended tire pressure. Then it sends that information to the air compressor to fill up the tires. When I looked at the air compressor I noticed that it read 45 PSI instead of 42. I was a little too shy in the moment to ask the attendant why there was a discrepancy but on the drive home, it hit me. Air expands as the temperature goes up and it’s a really hot day. That 42 PSI rating is meant for tires at room temperature. When I got home I did some quick math. It was 99° outside. Believe it or not, 45 PSI at 99° cools to almost exactly 42 PSI at room temperature (72°). This means that the little air compressor was taking into account the ambient air temperature and calculating a PSI offset when deciding how much air it should put in my tires. That’s so cool! I don’t know how common air compressors are that do that (I’ve never seen one) but it’s such a good idea. Whoever decided to put a thermostat on an air compressor was a fucking genius.

That’s it, that’s my TED talk. Thank you for reading.