An orange air quality alert means the Air Quality Index (AQI) has reached 101 to 150, a level the EPA classifies as “Unhealthy for Sensitive Groups.” At this level, most healthy adults can go about their day without problems, but people with certain health conditions, children, and older adults may start experiencing symptoms like coughing, throat irritation, or chest tightness.
What the AQI Numbers Mean
The Air Quality Index is a scale from 0 to 500 that measures how polluted the air is at any given time. It’s color-coded so you can quickly gauge risk: green (0 to 50) is good, yellow (51 to 100) is moderate, and orange (101 to 150) is where health effects begin showing up in vulnerable people. Above orange, the scale moves to red (151 to 200), which is unhealthy for everyone, and continues upward into purple and maroon for hazardous conditions.
The AQI tracks several pollutants, but the two most common triggers for orange alerts are ground-level ozone and fine particulate matter (PM2.5). The day’s AQI reading reflects whichever pollutant scores highest.
What Causes Orange Alerts
Ground-level ozone forms when vehicle exhaust and industrial emissions react with sunlight and heat. This is why ozone-driven orange alerts are most common on hot, sunny afternoons during summer months. The chemistry is straightforward: more heat and more sunlight mean faster reactions and higher ozone levels. Mornings and evenings typically have lower ozone concentrations.
Particulate matter alerts, on the other hand, come from smoke, dust, and airborne aerosols. Wildfire smoke is a major source, but construction dust, industrial activity, and traffic all contribute. Rain tends to wash particulate matter out of the air, while calm, stagnant conditions let it accumulate. Wind can either disperse pollution or, in the case of wildfires, carry it hundreds of miles from the source.
Who Is Most at Risk
The “sensitive groups” in an orange alert include a wider range of people than many realize:
- People with heart or lung disease, including asthma, COPD, and heart failure
- People with diabetes
- Children under 18, whose lungs are still developing and who tend to spend more time active outdoors
- Older adults, who have a higher prevalence of cardiovascular and respiratory conditions along with a gradual decline in the body’s natural defenses
- People with lower socioeconomic status, who may have less access to air conditioning, air filtration, or the ability to avoid outdoor work
If you’re a healthy adult without these risk factors, an orange alert day is unlikely to cause noticeable symptoms. But if you fall into any of these categories, even moderate outdoor activity can trigger problems.
Symptoms to Watch For
When the AQI enters the orange range, sensitive individuals may notice coughing, watery eyes, throat irritation, or a tight feeling in the chest when breathing. These symptoms happen because pollutants irritate and inflame the airways, causing them to narrow. Breathing becomes harder, especially during physical exertion.
The effects go beyond the respiratory system. Both ozone and particulate matter are associated with increased cardiovascular events, including stroke and heart attack. For people with existing heart conditions, an orange alert day carries real risk even if they don’t feel obvious respiratory symptoms.
How to Adjust Your Day
The core advice during an orange alert is to reduce prolonged or heavy physical activity outdoors if you’re in a sensitive group. That doesn’t necessarily mean staying inside all day. It means scaling back intensity: go for a walk instead of a run, take more frequent breaks, and shorten the time you spend exercising outside.
Timing matters, especially for ozone. Since ozone builds through the day and peaks in the afternoon and early evening, shifting outdoor activities to the morning can make a meaningful difference. Schools follow similar guidance from the EPA, moving recess and sports practices to morning hours or bringing activities indoors on orange days.
If you have asthma, keep your quick-relief inhaler accessible and follow your asthma action plan. The combination of polluted air and physical exertion is what drives most flare-ups, so reducing one or both of those factors lowers your risk considerably.
Protecting Indoor Air Quality
Staying indoors helps, but only if the air inside your home is actually cleaner than the air outside. On orange alert days, especially those driven by wildfire smoke or heavy particulate matter, close your windows and doors. If you have air conditioning, run it with a clean filter, and close the fresh air intake so the system recirculates indoor air instead of pulling in polluted outdoor air.
For better filtration, use filters rated MERV 13 or higher in your HVAC system. These are significantly more effective at trapping fine smoke and dust particles than standard filters. A portable HEPA air cleaner in the room where you spend the most time can create a pocket of much cleaner air, which is especially helpful if your home doesn’t have central air conditioning.
How Orange Differs From Red
The key distinction between orange and red is who’s affected. At orange (101 to 150), health effects are mostly limited to sensitive groups, and the general public is unlikely to notice anything. At red (151 to 200), everyone starts to feel the impact. Healthy adults without any pre-existing conditions can experience respiratory symptoms at the red level, and sensitive groups face more serious health risks.
This distinction matters for how you respond. An orange day calls for precautions if you’re in a vulnerable category. A red day means everyone should limit time outdoors, regardless of their health status.
Recent Changes to Air Quality Standards
In February 2024, the EPA tightened the annual standard for fine particulate matter from 12 to 9 micrograms per cubic meter, a significant change designed to protect millions of additional Americans from health effects like heart attacks and premature death. The agency also announced revisions to the AQI itself to better communicate particulate matter risks to the public. These changes mean some areas that previously hovered in the yellow range may now trigger orange alerts more frequently, reflecting a stricter understanding of what concentration of particles is safe to breathe over time.
You can check your local AQI in real time through the EPA’s AirNow website or app, and many weather forecasts now include air quality alongside temperature and precipitation. Setting up email or app notifications through AirNow lets you know before you head outside whether it’s a day to adjust your plans.