All homes let in some outside air, whether it is from doors opening or tiny cracks in windows. Doctors andair-quality researchersrecommend setting up what is called a “clean room” inside your house to help protect your health during the worst days. You designate one room in your home as your clean-air space, focus your air-improvement efforts there and spend much of your time in the room.

A clean room is a particularly good option for people at high risk from exposure to polluted air, including children, the elderly and those with underlying cardiac or pulmonary disease, says Dr. Stephanie Lovinsky-Desir, director of pediatric pulmonology at Columbia University Irving Medical Center.

Air-quality index levels in parts of the northeast on Wednesday reached above 300, a level considered hazardous even for those without underlying health problems. Anyone experiencing pollutant-induced symptoms such as cough, headache, mild shortness of breath and itchy eyes might benefit from a clean room, doctors say.

Setting up the clean room

Start by identifying a room where you will be willing to spend the most time. In a small apartment, this will be easy. In a multiroom home, look for a room with fewer windows or doors leading outside, says Rich Branson, a respiratory therapist and professor at the University of Cincinnati College of Medicine. The room should also be big enough for members of your household to congregate.

If you open a door to go outside, make sure the door to your clean room is closed first, he suggests. Stuff a towel into the cracks of any windows or doors in the room to minimize leakage.

Focusing on one room can be more manageable and realistic than trying to transform your entire home, says Jie Zhao, who leads a team of scientists at Delos Labs researching how to make indoor spaces healthier.

Experts broadly agree on one room you shouldn’t choose: your kitchen. Certain types of cooking oil can emit PM2.5, tiny particulate-matter pollutants that are the main pollutant of concern in the wildfire smoke blanketing the Northeast. Gas stoves can also produce another type of pollutant, nitrogen dioxide, that could further irritate the airways.

Using an air purifier

If you have an air purifier, the clean room is the place to put it, according to Environmental Protection Agency guidelines.

If you are considering buying an air purifier, health experts recommend a High Efficiency Particulate Air, or HEPA, filter that can remove the fine particulate matter in the wildfire smoke. A good quality air purifier ranges from approximately $100 to about $1,000.

It is fine to move your air purifier around based on where you are spending time in the house, such as taking it from your bedroom overnight to your living room or office room during the day, doctors say. If you need air-conditioning, check that your HVAC system is only recirculating air from within the home and not fresh air from outside.

Other precautions at home

Changing out of clothes you wore outdoors or showering before entering a clean room won’t hurt and might make you feel more comfortable, says Zhao, but it is unlikely to make much of a difference for your health.

Health professionals and the EPA also recommend avoiding other products that emit smoke and particles in your clean room when the air is bad, including many cleaning products and scented candles or incense. However, don’t panic if you can’t follow all of these recommendations perfectly. On the whole, short-term exposure to air pollution isn’t likely to cause acute harm unless people have underlying conditions such as asthma, says Dr. Elizabeth Joy, senior medical director of wellness and nutrition for Intermountain Healthcare in Salt Lake City.

Chronic exposure to air pollution has been linked to many health problems, including heart and lung disease, so doctors say it is good to have a plan in place if poor air-quality conditions persist.

“I think we’re not as accustomed to it on the East Coast being so severe, but we have to learn from what our West Coast colleagues have been doing to mitigate exposure,” says Columbia’s Lovinsky-Desir. “This is a real problem that we have to pay attention to.”