See map of where air quality is being affected by the Los Angeles wildfires

As fires burn across Los Angeles County, spurring thousands of evacuations, drifting smoke is affecting the L.A. area and beyond. Wildfire smoke can be harmful to health, especially for children, the elderly, those who are pregnant and people with respiratory or cardiovascular issues.

Hazardous air quality can affect people’s health in multiple ways, ranging from headaches and eye irritation to trouble breathing and even heart failure. Here’s how to tell if you’re in an area at risk.

What is the Air Quality Index, or AQI?

The Air Quality Index, often referred to as AQI, is a federal measure of the amount of air pollution, reported on a six-color spectrum from green (good) to hazardous (maroon). There are five pollutants evaluated as part of the index: ozone, particulate matter, carbon monoxide, sulfur dioxide and nitrogen dioxide. The index shows what health effects are associated with each category of air quality.

Map of AQI

Ways to protect your health when air quality is bad

Experts say the particles in wildfire smoke can cause headaches, irritate sinuses, make noses run and eyes water, among milder symptoms. Poor air quality also increases the risk of much more severe health issues, including stroke, heart attack and heart failure.

Experts say if you can, the best protection is to wear goggles and a half-face respirator with combined particle and gas cartridge. If you can’t, wear a high-quality mask, like an N95 mask — or at least a surgical mask or some kind of face covering. And if you’re able to stay indoors, do so, especially if you can run an air purifier or have filters on your HVAC system.