NEW YORK (PIX11) — The advice Wednesday and Thursday has been to stay inside. But what’s the best plan for air circulation in an indoor space with the windows closed?

Michael Blouin is a Petri, Plumbing, Heating and Cooling manager, which has been serving Brooklyn and surrounding New York City neighborhoods since 1906.

On Air Quality Alert days, ensure the unit is not drawing in the air from outside. Most products have a switch that can be set to recirculate the air inside the room.

“There is a damper that can close if you feel hot or cold air,” Blouin said.

The Air Quality Alert day can also serve as a reminder to check the filter and have the unit looked at by a crew or landlord.

Air purifiers are also an option. Dr. Deena Gupta-Adimoolam is an endocrinologist.

Doctors say the conditions outside and inside will affect most people somehow. People with existing health conditions are vulnerable. Others may experience irritation to the eyes, nose and throat.