New York City and Long Island periodically feel the effects of smoke from fires in Canada and elsewhere.

Your air-conditioning can help you keep smoke, ash and other unhealthy particulates from entering your home or business. Ash in particular causes wheezing, coughing, and difficulty breathing.

Here are recommendations from health officials that involve your heating, ventilation and air-conditioning system:

• Is your system equipped with a fresh air intake? If so, turn it to recirculate mode or close the outdoor intake damper to keep outside air from getting inside.

 • An HVAC system with an evaporative cooler is more complicated. If you can safely access it, “completely cover the outside air intakes with 4-inch-thick high-efficiency (MERV 13) furnace filters. Note: the external filters may need to be replaced frequently due to wind or rain damage,” says an advisory from the New York Department of Health and Mental Hygiene.

If you can’t do this, only use the evaporative cooler sparingly during smoky conditions. Otherwise it will  allow more smoke inside. As outdoor air quality improves, open windows to air out the house.

• Do not use a window air conditioner unless you can close the outdoor air damper, which lets outside air in. The seal between the air conditioner and the window should be as tight as possible.

• A portable air conditioner with a single hose, typically vented out of a window, can bring in more smoke. Use it only sparingly if the air is smoky.

• Do you have a portable air conditioner with two hoses? “Make sure that the seal between the window vent kit and the window is as tight as possible.”

Check the quality of outdoor air in your zip code at https://www.airnow.gov/