Apartment vs Single-Family Air Quality

The kind of home you live in changes what you breathe. Apartments and single-family houses each have characteristic problems, and the right fixes are different.

Why this matters

In apartments, your air is partly your neighbors' air. Studies from the Boston Housing Authority and others have found that 44 to 53% of multi-unit housing residents who don't allow smoking in their own home still experience secondhand smoke infiltration from elsewhere in the building. Cooking smells, fragrances, and pet allergens travel the same pathways.

In single-family homes, the air is more isolated, but you own all of it. Radon from the soil, gas furnaces in basements, attached garages, and ventilation that depends entirely on operable windows can drive up exposure if you don't manage it.

What the science says

Apartment-specific risks:

• A CDC-cited study found smoke transfer happens through wall penetrations (plumbing, electrical), shared hallways, stairwells, and shared HVAC. One paper documented smoke transfer into 2 of 14 "smoke-free" units and 6 of 8 hallways from adjacent smoke-permitted units.
• Multi-unit buildings often sit on busier urban arterials. Outdoor PM2.5 and NO2 averages are higher than for typical single-family lots.
• Higher floors do reduce traffic-related particles slightly, but cooking smells and recirculated radon can still reach upper floors through shared ducts.

Single-family-specific risks:

• The EPA estimates 1 in 15 US homes has radon at or above the 4 pCi/L action level. Basements are the usual source.
• Attached garages let vehicle exhaust and stored-chemical VOCs drift into living space, especially under negative pressure (running bath fans, dryer, or hood).
• Gas furnaces and water heaters in unsealed mechanical rooms can backdraft combustion gases when bath fans or hoods pull harder than the flue.
• Older homes (pre-1978) often have lead paint dust. Pre-1980 homes can have asbestos in old insulation, tiles, or popcorn ceilings.

What to do

If you're in an apartment

Find the smoke pathway and seal it. Smoke usually enters through outlets, around plumbing under sinks, baseboards, and the gap under the front door. Foam outlet gaskets ($5), backer rod and caulk around pipes, and a door sweep cost under $30 and cut infiltration substantially.

Run a HEPA purifier sized to the largest room you spend time in. Bedroom first, then main living space.

Set your bath fan and range hood to run a bit when cooking is heavy elsewhere. Slightly pressurizing your unit makes it harder for neighbor air to push in.

Talk to your building manager if smoke is steady. The American Lung Association has model letters and policy templates for advocating for smoke-free buildings.

Skip stove-top recirculating range hoods. They filter, they don't vent. In apartments where ducting outside isn't possible, a HEPA purifier in the kitchen does more.

If you're in a single-family home

Test for radon. EPA short-term test kits run $15 to $30. If you're above 4 pCi/L, install a sub-slab depressurization system ($1,500 to $3,000).

Keep the door to an attached garage closed and sealed. Weatherstripping and a self-closing hinge are the first fix. Don't store gas cans, paint, or solvents in there if you can help it.

Maintain combustion appliances. Service the furnace and water heater annually. Install a low-level CO monitor (alarms at 10 to 25 ppm, lower than the standard 70 ppm code minimum).

Ventilate intentionally. Run bath fans during and 20 minutes after showers. Run the range hood. Open windows on opposite sides of the house for 10 minutes when outdoor air is clean.

Check for backdrafting. Close all interior doors, turn on bath fans and the hood, then light a stick of incense near each combustion appliance flue. If smoke pulls down rather than up, you have a backdraft and need a pro to fix it.

Quick checklist

Apartment:

• Outlet gaskets, sealed pipe penetrations, door sweep
• HEPA purifier in bedroom and main room
• Bath fan and hood run during heavy cooking
• Building manager looped in on persistent smoke

Single-family:

• Radon test done in the last 2 years
• Garage door to house sealed and self-closing
• Low-level CO monitor (under 25 ppm alarm)
• Furnace and water heater serviced annually
• Backdraft check done

Sources

• Comparison of Indoor Air Quality in Smoke-Permitted and Smoke-Free Multiunit Housing
• American Lung Association: Is Secondhand Smoke Infiltrating Your Apartment
• CDC: STATE System Multiunit Housing Fact Sheet
• EPA: A Citizen's Guide to Radon
• Indoor Air Quality in Multi-Family Housing: Drivers and Interventions
• EPA: Indoor Air Quality and Combustion Pollutants
• The Effect of Floor Height on Secondhand Smoke Transfer in Multiunit Housing