How to read the air-quality index (AQI) scale, and why it can help you stay safe from wildfire smoke

• Wildfires are raging across Canada, and the smoke is being pushed southward.
• On June 7, extremely poor air quality turned the sky orange in NYC and other parts of the Northeast.

As wildfires rage across central Canada, the resulting smoke has caused air quality to worsen in parts of the Northeast region of the United States.

Unsettling images of orange skies in New York City on Wednesday shocked the public and raised widespread concern and confusion about the risks posed by poor air quality.

To determine the quality of the air, the Environmental Protection Agency (EPA) uses the air-quality index, or AQI. The scale spans from numbers 0 to 500. A higher AQI value signifies a higher level of air pollution and a greater health risk.

On June 7, AQI values of over 400 were recorded in New York City, according to the New York Times.

"The effects of air pollution can be mild, like eye and throat irritation, or serious, including heart and respiratory issues," reporter Adeel Hassan wrote for the Times. "They can also linger even after the air has cleared, as pollution can cause inflammation of the lung tissue and increase the vulnerability to infections," he added.

Here's a comprehensive guide to the AQI scale, including what the numbers mean and how you can protect yourself from harmful air pollutants during a wildfire.

0-50: Good

According to AirNow, a website and app run by the EPA, an air-quality index of or under 50 signifies satisfactory air. Air of this quality poses minimal to no risk to humans. It is highly unlikely that individuals who inhale air that falls at this point in the AQI will experiences health issues as a consequence.

51-100: Moderate

Air that falls between 51-100 on the AQI is deemed "acceptable" by the EPA. Individuals who are particularly sensitive to air pollution may be at risk if they inhale air of this quality.

According to the EPA, people with heart or lung disease; people with diabetes; older adults; and children, are groups generally more sensitive to air pollutants.

101-150: Unhealthy for sensitive groups

While it is still possible for members of the general population to experience side health issues stemming from this caliber of air quality, sensitive groups are still far more likely to be affected.

151-200: Unhealthy

The general population is more likely to experience health issues, and sensitive groups are at risk of serious health concerns.

201-300: Very unhealthy

The high risk of health concerns extends to the general public at this AQI level.

301-500: Hazardous

Everyone who inhales air that falls between 301-500 on the AQI scale is likely to be affected by the poor air quality.

How can I protect myself from air pollutants?

As Insider's Mia de Graaf previously reported, there are ways to protect yourself when the air quality is particularly poor. These include staying inside and closing your windows. Certain indoor activities should also be avoided, such as burning candles or fires, which increase indoor pollution, and vacuuming, which may kick up fine particles that have come inside the home.

If you must go outside, wearing an N95 mask can help filter the air you inhale.

"If you have to exert yourself, exert yourself less. Hydrate more," Dr. Leonardo Trasande, who studies environmental health at New York University, told The Associated Press.