Falling leaves and budding trees are semi-annual signals to inspect HVAC systems to make sure heating and air conditioning flow freely and efficiently. Some mechanical components, like the flue pipe that expels carbon monoxide, should only be checked by a professional. But you can eyeball other HVAC parts and save money on house calls and fuel bills.

Inspect filters

Air filters, which clean the air returning to your HVAC system, are the easiest and most obvious components to check. Yours should be dust and dirt-free because you’ve cleaned or replaced them once a month. (Ahem!) If you’ve fallen behind on air filter maintenance, vacuum or rinse them under a hose or faucet, or replace disposables.

Ductwork problems

Exposed duct work in your basement, attic, or Starbucks-style loft is easy to inspect. Look for:

• Peeling duct tape and loose fittings around seams

• Dirt streaks that indicate escaping air

• Dents in metal

• Collapsed or torn sections of flex ducts.

Furnace flames

Fire up your furnace and inspect the flame. It should be a steady blue, not a flickering yellow or orange, which indicates combustion problems that need professional help. Make sure side panels are closed and fastened.

Grills and registers

Inspect air return grills and HVAC registers for dust, dirt, and pet hair that impeded airflow. Open and shut registers to ensure they work. Make sure furniture hasn’t wandered over vents.

Air conditioning compressors

Be sure outside compressors are unobstructed by vines, shrubs, and leaves. Check that compressor fins are straight and undamaged. Place a level on top of units to detect a tilt, which hurts efficiency. If not level, slip a shim under the unit. Remove the top panel and inspect the blade for damage, but don’t repair a bent blade yourself: Call an expert to replace the blade ($200 to $300).

Thermostat check

Inspect thermostats by removing covers to sleuth out dust and dirt that can shorten the life of mechanisms. Remove particles by gently cleaning with a Q-Tip.

Lisa Kaplan Gordon is a managing editor for HouseLogic.