Frequently Asked Questions

The Air Quality Index (AQI) is a standardized indicator developed by the EPA that translates complex air pollution data into a simple number from 0 to 500. Think of it like a thermometer for air quality—higher numbers mean worse air and greater health concerns.

The AQI uses color-coded categories: Green (0-50) is Good, Yellow (51-100) is Moderate, Orange (101-150) is Unhealthy for Sensitive Groups, Red (151-200) is Unhealthy, Purple (201-300) is Very Unhealthy, and Maroon (301-500) is Hazardous.

The AQI tracks six major air pollutants regulated by the Clean Air Act:

• Ground-level ozone (O₃): Forms from reactions between pollutants in sunlight
• Particulate matter (PM2.5 and PM10): Tiny particles from combustion, dust, and other sources
• Carbon monoxide (CO): Colorless, odorless gas from incomplete fuel combustion
• Sulfur dioxide (SO₂): From burning fossil fuels at power plants and industrial facilities
• Nitrogen dioxide (NO₂): Primarily from vehicle emissions and power plants

The reported AQI is always the highest value among all monitored pollutants. That pollutant becomes the "primary pollutant" for that day.

Both are particulate matter, but differ in size:

• PM2.5: Fine particles 2.5 micrometers or smaller (1/30th the width of a human hair). These can penetrate deep into lungs and enter the bloodstream. More dangerous and harder to filter. Sources include vehicle emissions, wildfires, and industrial activities.
• PM10: Coarse particles 10 micrometers or smaller. Includes dust, pollen, and mold spores. Can irritate airways but don't penetrate as deeply. Generally filtered by nose and upper airways.

PM2.5 is typically the bigger health concern and often the primary pollutant during wildfire smoke events.

No. The AQI is not a linear scale. The number represents health risk categories, not proportional pollution levels. AQI 100 means you've crossed from "Good" into "Moderate" air quality, but it doesn't mean pollution doubled.

What matters most are the thresholds: 50 (good to moderate), 100 (moderate to unhealthy for sensitive groups), 150 (unhealthy for sensitive to unhealthy for all), etc. Each category jump represents increasing health risks.

AQI is typically updated hourly based on continuous monitoring from air quality stations. However, the frequency varies by location and data source:

• Real-time monitors: Update every hour or even more frequently
• AirNow.gov: Updates hourly for most locations
• AirQuality.directory: Updates hourly from OpenWeather's global monitoring network
• Forecasts: Typically provided once or twice daily for the next 24-48 hours

During rapid changes (like wildfire smoke arriving), check more frequently or enable AQI alerts on your phone.

Certain groups are more susceptible to air pollution's health effects:

• Children: Developing lungs, breathe more air per body weight, more outdoor activity
• Older adults (65+): More likely to have existing heart or lung conditions
• People with asthma or COPD: Airways already inflamed and sensitive
• People with heart disease: Pollution can trigger cardiovascular events
• Pregnant women: Pollution may affect fetal development
• Outdoor workers: Extended exposure during work hours
• Athletes and active individuals: Breathe more deeply and rapidly

If you're in one of these groups, start taking precautions at lower AQI levels (around 100 instead of 150).

Short-term exposure symptoms may include:

• Coughing or throat irritation
• Difficulty breathing or shortness of breath
• Chest tightness or pain
• Wheezing or asthma attacks
• Eye, nose, or throat irritation
• Headaches
• Fatigue or decreased exercise capacity

Long-term exposure can lead to chronic bronchitis, reduced lung function, heart disease, cancer, and premature death. If you experience severe symptoms, seek medical attention.

Yes, especially if you're sensitive or exposed long-term. While "moderate" suggests acceptable air quality for most people, research shows even these levels can affect:

• Sensitive individuals may experience minor respiratory symptoms
• Athletes may notice reduced performance
• Long-term exposure at moderate levels still increases health risks
• Some people are more sensitive than others

If you notice symptoms like coughing or shortness of breath during moderate AQI days, consider yourself sensitive and take precautions earlier.

Emerging research suggests yes. Studies have linked air pollution exposure to:

• Increased rates of anxiety and depression
• Cognitive decline and dementia risk
• Autism spectrum disorders (prenatal exposure)
• Reduced academic performance in children
• Overall decreased quality of life during prolonged poor air quality events

The mechanisms aren't fully understood but may involve inflammation, oxidative stress affecting the brain, and psychological stress from being unable to enjoy outdoor activities.

Yes, when properly selected and used. Quality air purifiers with true HEPA filters can remove 99.97% of particles 0.3 microns and larger, including PM2.5.

Key points:

• Must have true HEPA filter (not "HEPA-type" or "HEPA-like")
• Size purifier appropriately for room square footage (check CADR rating)
• Run continuously during poor air quality events
• Replace filters according to manufacturer recommendations
• Avoid ozone generators—these can make air quality worse

Studies show HEPA purifiers reduce indoor PM2.5 by 50-80% and provide measurable health benefits, especially during wildfire smoke events.

N95 and KN95 masks are effective for particulate matter (PM2.5, PM10, smoke, dust) but not for gases like ozone or carbon monoxide.

Effectiveness:

• N95/KN95 masks filter at least 95% of particles 0.3 microns or larger
• Studies show 60-70% reduction in PM2.5 exposure during wildfire events
• Proper fit is crucial—gaps around the edges reduce effectiveness dramatically

When masks help:

• Wildfire smoke (very effective)
• High PM2.5/PM10 days (effective)
• Dust storms (effective)
• High ozone days (NOT effective—ozone is a gas)

Cloth and surgical masks provide minimal protection from air pollution. Stick with N95 or KN95.

For most healthy adults, yes—the benefits of exercise generally outweigh the risks at moderate AQI levels. However, consider these factors:

• Time your workout: Early morning usually has better air quality
• Choose your location: Parks away from traffic are better than street running
• Reduce intensity slightly: Don't push for PRs on moderate days
• Listen to your body: If you feel unusually winded or irritated, cut it short

Sensitive individuals (asthma, heart disease, pregnancy) should consider moving workouts indoors when AQI exceeds 100. For everyone, avoid outdoor exercise when AQI hits 150+.

Not always. It depends on outdoor AQI:

• When outdoor AQI is good (0-50): Opening windows is great for fresh air and ventilation
• When outdoor AQI is moderate (51-100): Opening windows during cooler parts of day is usually fine
• When outdoor AQI is unhealthy (100+): Keep windows closed; you're bringing pollution inside

During poor air quality events, sealed windows + HVAC with good filters + air purifiers will give you better indoor air quality than opening windows.

For most people, true HEPA filters are the gold standard:

• HEPA filters: Remove 99.97% of particles ≥0.3 microns (PM2.5, pollen, dander, mold spores)
• Activated carbon: Adds odor and gas removal (cooking smells, VOCs)
• Combined HEPA + carbon: Best for comprehensive air cleaning

Avoid:

• Ionizers (can produce harmful ozone)
• Ozone generators (dangerous, can worsen air quality)
• "HEPA-type" or "HEPA-like" (marketing terms, not true HEPA)
• UV-C alone (doesn't remove particles)

Look for units certified by AHAM (Association of Home Appliance Manufacturers) with appropriate CADR ratings for your room size.

Ground-level ozone forms through chemical reactions between nitrogen oxides (NOₓ) and volatile organic compounds (VOCs) in the presence of sunlight and heat. Summer provides perfect conditions:

• Longer, more intense sunlight
• Higher temperatures accelerate chemical reactions
• Stagnant air conditions trap precursor pollutants
• More driving (vacations, road trips) increases NOₓ emissions

Ozone typically peaks between 2-8 PM on hot, sunny days. This is why summer afternoons often have the worst air quality in many cities.

Wildfire smoke can travel thousands of miles:

• Smoke from western U.S. fires regularly reaches the East Coast
• Canadian wildfires have impacted air quality across the entire eastern U.S.
• Smoke plumes can circle the globe in the upper atmosphere
• Fine particles (PM2.5) stay suspended in air for days or weeks

This means you can experience poor air quality from fires burning 1,000+ miles away. Always check your local AQI, even if there are no nearby fires.

While ozone decreases in winter, other pollution sources emerge:

• Wood smoke: Fireplaces and wood stoves emit heavy PM2.5
• Temperature inversions: Cold air trapped under warm air prevents pollution from dispersing
• Vehicle cold starts: Engines emit more pollutants when cold
• Reduced ventilation: Buildings sealed tight concentrate indoor pollution

Valley cities (Salt Lake City, Bakersfield, Phoenix) often experience their worst air quality during winter inversions, which can last days or weeks.

AirQuality.directory uses data from OpenWeather's global air quality monitoring system, which combines:

• Satellite observations of atmospheric conditions
• Advanced atmospheric modeling
• Ground-based monitoring station data

Data is updated hourly and covers all major pollutants including PM2.5, PM10, ozone (O₃), nitrogen dioxide (NO₂), carbon monoxide (CO), and sulfur dioxide (SO₂).

You might see slightly different AQI values from different sources due to:

• Different monitoring locations: AQI can vary significantly within a few miles
• Update timing: Sources update at different frequencies
• Calculation methods: Some use NowCast (weighted recent readings), others use direct measurements
• Data sources: Different networks of monitors (EPA, PurpleAir, OpenWeather)

Small differences (±10-20 AQI points) are normal and usually don't change the health category. Large discrepancies might indicate one source is more accurate for your specific location.

Personal monitors can be useful if:

• You live far from official monitoring stations
• You want to measure indoor air quality
• You're very sensitive to pollution and need hyperlocal data
• You're testing effectiveness of air purifiers or other interventions

Considerations:

• Quality varies widely—research reviews before buying
• Consumer-grade sensors can be less accurate than professional monitors
• Need regular calibration
• Cost ranges from $200-$500+ for decent units

For most people, using free online AQI sources like AirQuality.directory or AirNow.gov is sufficient.

It depends entirely on current AQI. General guidelines:

• AQI 0-100: Generally safe, though sensitive people should watch for symptoms
• AQI 101-150: Reduce intensity and duration; sensitive groups should stay indoors
• AQI 151-200: Avoid outdoor exercise for everyone
• AQI 201+: Minimize all outdoor exposure, even non-exercise activities

During fire season, check AQI before every outdoor workout. Conditions can change rapidly as smoke moves in and out of your area.

Children are especially vulnerable. Protect them by:

• Checking AQI before outdoor play and sports practice
• Keeping them indoors during AQI > 100
• Running air purifiers in bedrooms and play areas
• Timing outdoor activities for better air quality (early morning)
• Advocating for air quality policies at schools
• Teaching older children to check AQI themselves

If your child has asthma, work with their doctor to adjust action plans for poor air quality days.

Not recommended. Wilderness areas often lack the protective measures available at home (air purifiers, sealed buildings). During poor AQI:

• Vigorous hiking increases pollution intake when you're breathing heavily
• No ability to shelter from smoke
• Risk of being caught in worsening conditions far from medical care
• Camping in smoke is unpleasant and unhealthy

Monitor forecasts before trips and be prepared to postpone if AQI is projected above 100. Flexibility is key during fire season.

If smoke or poor air arrives suddenly while you're outdoors:

• Get indoors as quickly as safely possible
• If driving, close windows and use air recirculation mode
• Reduce physical exertion—walk don't run
• Cover nose and mouth with a cloth (limited protection, but better than nothing)
• If you have an N95 mask, put it on
• Once indoors, remove and wash clothing that was exposed to smoke

If you're far from shelter and must remain outdoors, reduce activity level and breathe through a dampened cloth. Seek medical attention if you experience severe symptoms.