Air Quality Health Index
Last updated: July 24, 2023
The Air Quality Health Index (AQHI) provides hourly air quality readings and related health messages. The AQHI reports on the health risks posed by a mixture of pollutants, including:
- Particulate matter (PM2.5)
- Ground-level ozone (O3)
- Nitrogen dioxide (NO2)
The rating for the AQHI is based on the combination of the health risks from each of the pollutants in the index. This method differs from the older Air Quality Index (AQI), which determined air quality based on the highest value of only one pollutant.
British Columbians can use the AQHI to check the quality of outdoor air before heading off to work or play.
How to use the AQHI
The Air Quality Health Index is available to more than 80 percent of B.C.'s population in 25 communities.
- View the full list in the left-hand navigation
- Illustrates the level of health risk with a number and colour scale of 1 to 10 or higher
- Labels the health risk as low, moderate, high or very high
- Provides the predicted air-quality health risk over the next 36 hours
- Provides advice on minimizing the health risk from air pollution
Air Quality Health Index and wildfire smoke frequently asked questions (FAQ)
The AQHI is measured on a scale of 1 (low) to 10+ (very high). The AQHI index values are grouped into four categories that help you to easily and quickly identify your level of health risk:
- Low Health Risk: AQHI values from 1 to 3
- Moderate Health Risk: AQHI values from 4 to 6
- High Health Risk: AQHI values from 7 to 10
- Very High Health Risk: above 10 (A very rare occurrence usually connected to wildfire smoke)
The AQHI is calculated based on the combination of health risks from common air pollutants that are known to harm human health. These pollutants are:
- Fine Particulate Matter (PM2.5): microscopic solid or liquid particles, suspended in the air, with a size of 2.5 micrometers (milionth of a meter) or less (about 1/30th the diameter of a human hair)
- Ground Level Ozone (O3): a gas formed in the atmosphere from reactions involving nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight
- Nitrogen dioxide (NO2): a reddish-brown gas that is associated with emissions from vehicles and other fossil fuel combustion processes
The AQHI is available year-round in 14 communities, accounting for more than 80 percent of the population in British Columbia.
The best way to use the AQHI during the wildfire season is to regularly check the current index value and the forecast maximum for the day as conditions can change rapidly.
PM2.5 is a major component of wildfire smoke. If you have a PM2.5 monitor in your community, you can check the PM2.5 reading to give you an idea of how smoky it is.
You can use the current map of fine particulate matter concentrations (PM2.5) to find a monitoring station in your community.
You can also view wildfire smoke forecasts from:
Every hour, air monitoring stations typically report hourly averages of PM2.5 concentrations. The one-hour averages provide valuable information on rapid changes in PM2.5 levels and are essentially used to calculate the AQHI.
Based on the available one-hour averages, 24-hour averages of PM2.5 concentrations are then determined in 2 ways:
- A 24-hour running average is obtained every hour as the average PM2.5 concentration over the previous 24 hours, which is used for air quality advisories
- A daily average is also calculated based on PM2.5 concentrations over 24 hours, midnight-to-midnight, for any given day
To gauge air quality, 24-hour PM2.5 averages are compared to the provincial Air Quality Objective of 25 μg/m3 (micrograms per cubic meter of air).
Air Quality Objectives (AQOs) are limits on the acceptable level of contaminants in the air, established by government agencies to protect human health and the environment.
Whenever the 24-hour PM2.5 average exceeds the objective, that typically indicates poor air quality.
For more information on provincial Air Quality Objectives, review BC Ambient Air Quality Objectives (PDF, 227KB)
- Latest summaries of PM2.5 status in BC air zones, as well as the annual and 24-hour PM2.5 levels at individual monitoring stations, can be found at: Status of Fine Particulate Matter in BC
- Read individual Air Zone reports on the achievement of the Canadian Ambient Air Quality Standards for ground-level ozone and fine particulate matter in B.C.
- View the annual BC Lung Association’s State of the Air Reports
Wildfire smoke is made up of many gases and small particles. This can change depending on what is burning, distance from the fire, weather conditions and fire temperature.
Fine particulates are usually the main components of wildfire smoke. These are microscopic solid or liquid particles, suspended in the air, with a size of 2.5 micrometers (millionth of a meter) or less (about 1/30th the diameter of a human hair). Due to their small sizes, it takes significantly longer than larger particles to be removed from the air.
Given the ability to penetrate deep into the respiratory system and even the bloodstream, PM2.5 is considered the biggest public health concern from outdoor air pollution in BC.
For more information on particulate matter and wildfire smoke visit:
A Smoky Skies Bulletin is a public advisory with the purpose of communicating the quickly changing nature of wildfire smoke.
These bulletins notify the public when wildfire smoke is likely to affect air quality in their region within the next 24 to 48 hours. A Smoky Skies Bulletin is issued, updated and ended based on the available information from PM2.5 monitoring stations, smoke forecast models, weather forecasts, satellite imagery, as well as visual observations.
Metro Vancouver and the Fraser Valley Regional District issue their own Air Quality Advisories.
Given that smoke conditions can change rapidly, relocating to another community may not always help you reduce your exposure.
Emergency BC recommends that sheltering-in-place (staying where you are) is often the best way to reduce your exposure to wildfire smoke, but only if you have access to clean indoor air in your home or community.
Visit Emergency Info BC for more information on protecting your physical and mental health during the wildfire season.
Planned events during the wildfire season will not necessarily be cancelled due to high AQHI readings. Organizers may decide to cancel events when the AQHI indicates 'high' to 'very high' health risks.
Organizers may provide alternatives to outdoor events, such as moving an event indoors, altering the duration, or postponing until the smoke has cleared. The AQHI can be used as a tool to make personal decisions for your activities and decide whether to attend outdoor events when the sky is smoky.
More information on cancelling or modifying outdoor events during the wildfire season can be found here:
If you are caring for groups of children during a wildfire season, such as summer camps, you can prepare by having established a smoke plan so that you can make clear and transparent decisions in smoky conditions.
In addition to consulting with your regional health authority, see the following information for those caring for children during smoke events:
- Childcare facilities and wildfire smoke – Vancouver Health Authority
- Considerations for Poor Air Quality Events – Northern Health
- Evidence Review: Reducing time outdoors during wildfire smoke events – BCCDC
Smoke can enter buildings through windows, vents, air intakes and other openings. Portable air cleaners can be used to reduce the impacts of wildfire smoke indoors.
The BC Centre for Disease Control (BCCDC) offers information on the use and purchasing of Portable Air Cleaners for Wildfire Smoke.
To understand the hazards associated with smoke and working conditions refer to WorkSafeBC’s Wildfire smoke: frequently asked questions.
Visit BC Center for Disease Control for information on the use of face masks for wildfire smoke.
Take the time to inform yourself of the resources available to you during the wildfire season and have important information readily available.
Relevant information is available from these resources:
The best resource for health information during the wildfire season is your Regional Health Authority.
People with symptoms should go to their health-care provider, walk-in clinic or emergency department depending on the severity of symptoms.
For general information about smoke, contact HealthLink BC:
- By phone: 811 - toll-free, 24 hours a day, 7 days a week
- Online: HealthLink BC
The First Nations Health Authority also provides information and support for Recognizing and Addressing Trauma and Anxiety During Disasters.
If you or a loved one is experiencing a medical emergency, call 9-1-1.
For questions related to air quality in B.C. contact the Ministry of Environment and Climate Change Strategy at BCairquality@gov.bc.ca.
Contact AQInfo@metrovancouver.org for air quality questions or concerns within Metro Vancouver.
For health-related questions, contact your Regional Health Authority.
Smoke and AQHI adjustments
Elevated smoke concentrations have been shown to sometimes cause the AQHI to under-report health risk. Therefore an adjustment to AQHI, called AQHI-Plus, is being made in B.C. to improve the accuracy of the reported health risk from smoke throughout the year.
The adjustment started as a pilot in May 2018 and adopted in B.C. in March 2021 following successful pilot and peer-reviewed health studies supporting its application.
The Air Quality Health Index Variation across British Columbia (PDF, 149KB) report is an overview of the AQHI and how it was developed to provide British Columbians with an estimate of short-term health risk caused by degraded air quality.
To receive more information, contact the B.C. Air Quality team and include 'Information on AQHI and AQHI-Plus' in the subject line.