First, make sure home is the right place to stay
A filtered room does not override an evacuation order. Follow local emergency alerts. If your home is too hot, smoky air is making you ill, or you cannot keep the space cool, look for a safer place with cooling and cleaner air. Colorado health officials advise against closing up a home if doing so makes it dangerously warm. Check Colorado wildfire smoke guidance and the AirNow Fire and Smoke Map for current information. This article does not report today's conditions.
People with heart or lung conditions should have a smoke plan with their health care provider. Seek medical attention for severe or worsening symptoms. An HVAC recommendation cannot decide whether it is medically safe for you to remain at home. EPA smoke and heat guidance.
Make one room easier to protect
Choose a room big enough for the people using it, with a door you can close. A bedroom can work well because you spend hours there. Keep its windows and doors closed during smoky periods, while preserving a clear way out. Put an air cleaner in that room and spend more time there when outdoor smoke is heavy. Keep it comfortable enough to use.
EPA calls this a clean room. It means a space with lower smoke levels, not a promise of smoke-free air. Keep the air cleaner running continuously, at the highest setting you can comfortably use. EPA clean-room instructions.
Choose capacity, not a big number on the box
A HEPA air cleaner can capture fine smoke particles. Interagency particle-filtration guidance. Check its smoke CADR, or clean air delivery rate. That number tells you how much filtered air it delivers. It matters alongside the filter type.
For wildfire smoke, the Association of Home Appliance Manufacturers recommends a smoke CADR at least equal to the room's area in square feet. For example, a 12-by-15-foot room has 180 square feet, so use a smoke CADR of at least 180 as a starting point with an 8-foot ceiling. Higher ceilings need more capacity. An open living area needs sizing for the connected space, not just the patch of floor around the unit. AHAM sizing guidance.
Check the speed used for that rating. CADR is usually measured at the highest speed. A quiet sleep setting moves less air. EPA speed-rating guidance. Leave the inlet and outlet clear of furniture and curtains. One small unit should not be counted on to clean several closed bedrooms. Interagency room-cleaner placement guidance.
Choose a device that does not produce ozone. Ozone irritates lungs. Avoid ozone generators, and check ozone testing for products using ionization or other electronic cleaning features. EPA ozone guidance.
Let the furnace filter help, if it fits the equipment
EPA recommends MERV 13, or the highest filter rating your equipment can accommodate. MERV describes particle-filtering performance. The correct choice also depends on the fan, filter slot, and airflow. A higher number alone does not establish compatibility.
Use the correct filter size and a snug fit. Do not crush a filter into the slot. If compatibility is unknown, ask a qualified HVAC professional to check the equipment and airflow before upgrading. During heavy smoke, check filters more often and keep replacements on hand. EPA wildfire filtration guidance.
With a suitable filter and properly operating equipment, setting the thermostat fan to On instead of Auto increases filtration between heating or cooling calls. Longer fan operation uses electricity and can affect moisture control during cooling. It needs to fit your home and equipment. EPA filter and fan guidance.
Check how your cooling brings air inside
During smoke, use the documented recirculation setting or close a controllable fresh-air intake. If you cannot identify the correct control, get help rather than covering an unknown opening.
Evaporative coolers bring outdoor air in. Single-hose portable air conditioners can also draw more smoky air into the home. Mini-split and window-unit filters generally are not designed to capture fine smoke particles, so a separate air cleaner still matters. The plan must preserve cooling, not simply shut it off. EPA equipment and heat guidance.
Avoid adding particles, and restore ventilation when air improves
Skip candles, incense, smoking, vaping, and aerosol sprays. Limit frying and broiling. Avoid vacuuming unless the vacuum has a HEPA filter. EPA indoor smoke-reduction guidance, EPA clean-room cleaning guidance. Damp wiping or mopping helps keep settled particles from returning to the air. Interagency damp-cleaning guidance.
When outdoor air improves, air out the home as conditions allow. Interagency ventilation guidance. A particle filter does not remove carbon dioxide from people breathing, and it cannot substitute for ventilation indefinitely. Other gases need different controls; no ordinary purifier removes every pollutant. ASHRAE carbon-dioxide guidance, EPA filtration limits.
Your next step: measure the room, check the air cleaner's smoke CADR, and find the approved filter requirements for your heating and cooling equipment. Those three facts make the next choice clearer before you spend more money.