Why these units hold on to odor

A window or through-wall air conditioner recirculates room air across a cold coil. Moisture condenses on that coil, and the damp surface catches smoke residue and dust very efficiently. Inside the cabinet there is usually foam insulation, a plastic drain pan and a blower wheel, all of which pick up film over time. None of it is visible when the unit is off.

The pattern is predictable. A smoker's unit is turned over in winter, when nobody runs the air conditioning. The walls get cleaned and painted, and the unit passes inspection. In June the new resident turns on the cooler, and the room fills with a stale, slightly damp ashtray smell. Because the walls are clean, people blame the paint or the building, when the source is sitting in the window.

In Capitol Hill buildings, many window units are landlord-owned and stay with the apartment from tenant to tenant. That makes them a turnover item, not something to leave for the next resident to discover.

Clean it or replace it?

There is no single rule, but these points usually tip the decision.

Cleaning may be enough when

  • The unit is fairly new and in good working order
  • The smoker lived there a short time
  • The coil can be reached and cleaned without dismantling the cabinet
  • There is no visible mold or heavy buildup in the drain pan
  • A test run after cleaning produces no noticeable odor

Replacement often makes sense when

  • The unit is old, inefficient or noisy anyway
  • Years of heavy smoking stained the front grille and filter frame
  • Internal foam or insulation smells when you sniff the cabinet
  • Odor returns after a careful cleaning
  • Cleaning would cost a large share of a new unit

Turnover steps for landlord-owned cooling units

Unplug the unit before any cleaning. For built-in or hardwired units, follow the manufacturer's instructions or use a qualified technician.

  • Remove and wash or replace the filter; a stained filter frame is a clue to the coil's condition.
  • Clean the front grille and cabinet exterior with a degreasing cleaner.
  • Have the evaporator coil cleaned with a coil cleaner suitable for the unit, following the product's directions.
  • Clear and clean the drain pan and drain path so standing water does not add musty odor to the smoke.
  • Check foam seals and the accordion side panels on window units; these are inexpensive to replace and often hold residue.
  • For through-wall units, clean the wall sleeve and check the gap between sleeve and wall for open paths to the outside or another unit.
  • Run the unit for an hour in the closed apartment during the final walkthrough.

Common questions

Can an ozone treatment fix an air conditioner?

It may reduce odor inside the cabinet, but it does not remove the film from the coil. Physical cleaning comes first; discuss any whole-unit treatment with whoever is doing the work.

General information for Capitol Hill, not a quote or professional advice. In an emergency, call 911.