() Los Angeles County residents affected by the wildfires that began burning this week are advised to wear the correct masks to protect themselves against harmful smoke.

Health experts have determined N95 respirator masks offer the best protection when worn correctly and fit properly.

The masks are readily available at hardware stores and pharmacies, and they can filter out fine particles found in smoke that irritate eyes, noses, throats and lungs, according to public health officials.

However, they do not protect against hazardous gases that are sometimes present in smoke.

Guidance provided by the New York City Health Department suggests residents exposed to conditions like those in Los Angeles County should wear masks when outdoor air quality is poor. Symptoms such as coughing or throat and eye irritation are often connected to air pollution exposure, and wearing a mask may help to reduce those symptoms, health officials said.

However, people should not wear a mask if they are unable to wear it correctly. An improperly fitted mask provides little to no filtration and makes the wearer feel they are protected when they are not. To be effective, masks should be worn to snugly cover the user’s nose, mouth and chin.

In addition to wearing a mask properly, ensuring the right mask is being used is also critical, according to health officials.

Single-strap paper dust and surgical masks do not adequately protect from wildfire smoke. Health officials also warn that bandanas or towels (wet or dry) should not be used as a mask. Although these face coverings may relieve dryness, they will not protect the lungs from wildfire smoke.

Health officials warn that anyone living with lung or heart disease or who is chronically ill should check with their doctor or health care provider before wearing a mask. The use of respiratory masks can make it more difficult to breathe and can make it uncomfortable to use them for longer periods of time.

An N95 mask blocks against 95% of fine particles, while an N90 mask protects the user from 90% of pollutants. When possible, masks should be certified by the National Institute for Occupational Safety and Health. These masks will be designated with printed markings to show they are authentic.

Although N100 or P100 filters can block out 99.7% of particles found around wildfires, the masks can make breathing difficult, Dr. William Lang, chief medical officer at WorldClinic and a former director of the White House Medical Unit, told Healthline.

If an N95 mask cannot be obtained, KN95 masks are equally effective in blocking particles associated with wildfires, Healthline reported.

Parcil Safety reported air quality levels will determine if it is necessary to wear a mask. The Air Quality Index is a numerical scale used to measure and report the quality of the air outdoors. It also offers information about the air pollution levels and how those levels could affect human health.

“The AQI typically measures several common air pollutants, including particulate matter (PM2.5 and PM10), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO),” the Parcil Safety website said. Each pollutant is assigned a specific index value based on its concentration in the air.

Each level of air quality is color-coded on the AQI, ranging from green (minimal to no health risks) to maroon (hazardous). Hazardous and very unhealthy levels (purple) indicate there is a higher risk of serious health effects for the entire population.

The most effective protection remains to stay indoors and limit outdoor activity during smoky conditions, health officials said. Those who must be outside should take frequent breaks, as breathing through respirator masks requires more effort.