When wildfire smoke is outside, the goal is to reduce the amount that enters your home while continuously filtering the air already indoors. This checklist explains how to adjust an air conditioner, inspect HVAC filtration, use portable air cleaners, limit ventilation that pulls in smoke, monitor indoor conditions, and decide when it is safe to bring in outdoor air again.
Overview
Wildfire smoke can enter through open windows, doors, gaps around frames, ductwork, and mechanical ventilation. Even a home with central air conditioning can experience poor indoor air quality if the system brings in outdoor air, if the filter does not fit correctly, or if smoky air enters whenever someone leaves a door open.
During a smoke event, treat the home as a controlled-air space. Keep windows and exterior doors closed as much as practical, run air conditioning in a mode that recirculates indoor air, and use filtration sized for the room or HVAC system. If your equipment has a fresh-air intake, outdoor-air damper, or ventilation mode, consult the equipment manual before changing it. Some systems require outdoor air for normal operation, and settings vary by model.
Do not rely on cooling alone to remove smoke. An air conditioner may lower temperature without removing enough fine particulate matter. Filtration is the key function to evaluate. For a detailed seasonal tracking routine, see the seasonal indoor air quality checklist.
What to track
1. Outdoor conditions
Check the local air-quality report before opening windows, exercising outdoors, or changing ventilation settings. Record whether conditions are improving, worsening, or fluctuating. A brief improvement does not always mean smoke has cleared for the day, so use the broader trend and any local health or emergency guidance rather than relying on a single reading.
2. Air conditioner and HVAC settings
For central air conditioning, select recirculation if that option is available. Keep the system fan in an operating mode that allows the filter to work, but balance runtime against energy use and the equipment manufacturer's instructions. Inspect thermostats, return grilles, and supply vents for unusual dust or visible residue.
If your home has a ducted fresh-air system, energy-recovery ventilator, whole-house fan, or attic fan, identify how it exchanges air before using it. A whole-house fan is designed to pull outdoor air through the home and is generally unsuitable when outdoor smoke is the problem. The guide to whole-house fans and attic fans can help distinguish their operating roles.
3. Filter condition and fit
Check the HVAC filter for loading, damage, and gaps around the frame. Smoke can make a filter appear dirty sooner than expected, but color alone is not a reliable measure of performance. Replace it according to the manufacturer's instructions or sooner if it is visibly loaded, damaged, or restricting airflow.
Use the highest-efficiency filter your HVAC system is designed to handle. A higher-rated filter is not automatically better if it causes inadequate airflow, noise, icing, or equipment stress. Confirm the required dimensions and compatibility in the owner's manual or with a qualified HVAC professional. The filter should fit snugly so air cannot bypass it.
4. Portable air cleaners and indoor readings
Place a portable air cleaner in the room where people spend the most time, such as a bedroom or living area. Choose a unit rated for that room size, keep its air inlet and outlet unobstructed, and run it at a speed that is practical for continuous use. If smoke is severe, one cleaner may not adequately serve several closed rooms.
An indoor particle monitor can show whether conditions change when the HVAC system, cleaner, windows, or doors are used. Place the monitor away from cooking, candles, direct airflow, and exterior doors. Treat readings as trend information rather than a guarantee that the air is safe, because consumer monitors vary and may not detect every pollutant.
5. Exhaust fans and entry points
Limit bathroom exhaust fans, kitchen range hoods, and clothes-dryer use to necessary tasks while outdoor smoke is heavy. These appliances exhaust indoor air and can draw smoky air inward through leaks. Avoid cooking with high-heat methods when possible, because indoor particles can add to the pollution already present.
Close the door between the main living area and a garage, inspect obvious gaps around exterior doors, and avoid opening windows for cross-ventilation. If you use a portable air conditioner, check that its window kit is sealed; the portable AC window-venting guide covers common setup and sealing issues.
Cadence and checkpoints
Use a short checklist whenever smoke arrives, then repeat the most important checks at least once a day while conditions remain poor:
- Check the outdoor air-quality trend and any local advisories.
- Confirm windows and exterior doors are closed.
- Verify the air conditioner is not unintentionally using a high-outdoor-air or ventilation mode.
- Inspect the HVAC filter and confirm that it is seated correctly.
- Run portable air cleaners in occupied rooms and keep them clear of furniture or curtains.
- Review the indoor particle reading, if available, at a consistent location.
- Limit unnecessary exhaust-fan use and indoor particle sources such as candles, smoking, and heavy frying.
After a prolonged smoke event, inspect filters again even if they were recently replaced. Clean only the components the manufacturer identifies as washable, and never wet electrical parts. If the HVAC system develops weak airflow, unusual noise, icing, or persistent odors, turn to the equipment manual or arrange professional troubleshooting rather than forcing the system to run.
How to interpret changes
If the indoor particle level rises soon after a window or door opens, the building envelope is likely allowing outdoor smoke inside. Close the opening, allow filtration to run, and compare the next reading after conditions stabilize. If indoor levels remain elevated with everything closed, look for additional sources: cooking, candles, fireplaces, smoking, dusty returns, or an operating ventilation system that brings in outdoor air.
If the air conditioner runs but the indoor reading does not improve, cooling is not the same as particle removal. Check whether the system actually moves air through a filter and whether the filter is compatible and properly installed. A portable air cleaner may be more effective for a single occupied room than relying on a central system with limited fan runtime.
Persistent smoke odor can remain in fabrics, carpets, and furnishings after particle levels fall. Ventilate only when outdoor conditions have improved enough to make that tradeoff reasonable. Avoid masking the odor with sprays, fragrances, or ozone-producing devices, which can add unwanted indoor pollutants.
When to revisit
Revisit this checklist whenever outdoor air conditions change, after opening windows, following a power outage, or when someone notices a new odor, haze, or breathing irritation. At the start of smoke season, confirm the HVAC filter size, purchase replacement filters, test portable air cleaners, and review each fan's purpose. Replace or clean equipment components only as directed; maintenance guidance for portable cooling equipment is available in the portable air cooler maintenance checklist.
After the event, return ventilation equipment to its normal settings only after outdoor air has improved. Open windows briefly when appropriate, monitor the indoor trend, and close them again if conditions deteriorate. Keep a simple record of filter changes, indoor readings, and equipment settings. That record makes the next smoke event easier to manage and can reveal whether your home needs better filtration, tighter window sealing, or a professional HVAC assessment.
If anyone in the home develops significant or worsening breathing symptoms, follow appropriate medical advice and seek urgent help when necessary. Home filtration supports cleaner indoor air, but it is not a substitute for emergency care or local public-safety instructions.
