CHICAGOLAND (CBS)–Dropping temperatures increased calls to Chicago area heating and cooling companies as furnaces kicked in for the first time overnight.

WBBM Newsradio’s John Cody reports overnight temperatures in the mid 30s started phones ringing in Chicago area heating and air conditioning services.

The president of South Suburban Heating and Cooling says most of the calls came from people who found their furnaces didn’t kick in when temperatures dropped to the mid-30s, usually those who’d been neglecting regular maintenance.

Dave Meter says the most useful thing the homeowner can do is do an eyeball check on the air filter to make sure air’s getting through.

“Absolutely. It’s the most important thing before you start up your furnace. The first thing you want to do is check your filter. If it hasn’t been replaced, or cleaned, or maintained in the last thirty days, you want to take care of that first. That’s the most important thing in your comfort system,” Meter says.

LISTEN: WBBM Newsradio’s John Cody reports

“What I do is hold it up to a light, and if you can still see a lot of light through it as if it was new, probably okay for a little while. But most filters, it’s pretty obvious.”

Meter says a musty heat odor when the furnace first kicks in isn’t a problem – explaining it’s just the furnace heating off particles collected on the heat exchanger over the summer.