Carbon monoxide is different from carbon dioxide
CO is carbon monoxide, a colourless, odourless gas associated with incomplete combustion. It is different from CO₂, carbon dioxide. Outdoor sources include vehicles and other combustion processes; dangerous indoor accumulation can arise from combustion equipment under unsuitable conditions.
How it affects the body
Breathing elevated CO reduces the blood’s ability to carry oxygen to organs such as the heart and brain. People with some forms of heart disease can be especially vulnerable. The effect depends on concentration and duration, and cannot be inferred from a PM2.5 value or a particle-pollution study.
Use the correct units and exposure period
CO is often reported in mg/m³ or ppm, unlike the µg/m³ commonly used for particles. Those numbers must not be compared directly. Standards and guidelines can refer to one-hour, eight-hour or daily periods, so a current hourly estimate is not evidence of every possible threshold exceedance.
An outdoor app is not an indoor safety alarm
Follow applicable outdoor advisories, but do not interpret a favourable map as proof that a building is safe. Closing windows or staying indoors is not a universal response to CO. A household CO alarm and the appropriate response to a suspected indoor incident serve a different purpose from outdoor monitoring; particle filters do not remove CO.
Sources
- US Environmental Protection Agency. Basic Information about Carbon Monoxide (CO) Outdoor Air Pollution. US EPA ↗
- US Environmental Protection Agency. Carbon Monoxide's Impact on Indoor Air Quality. US EPA ↗
- World Health Organization. WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. World Health Organization (2021) ↗
- National Institute for Occupational Safety and Health. Filtering Facepiece Respirators. CDC / NIOSH ↗
Educational information; personal health questions belong with your clinician.
Explore next
- SO₂: short-term exposure and sensitive airways
- Pollution masks: filter performance and facial fit are different
- NO₂: nitrogen dioxide and the airways
- Ground-level ozone: why exercise can change exposure
The 48-hour forecast is part of Atmiq Premium in the app. Get Premium →