Understand the air around you.

AQI converts pollutant measurements into a color-coded health scale. Learn what the number means, how it is calculated, and why AQI systems differ.

Understand the US AQI scale from Good to Hazardous, including category ranges, colors, health meaning and practical precautions.

Compare PM2.5 and PM10 by particle size, sources, health relevance, guideline values and what each reading means.

Use AQI, pollutant information and local guidance to plan children’s play, school activity, commuting and cleaner indoor air on poor-air days.

Use AQI, the dominant pollutant, exercise intensity and route to make safer decisions about running, cycling and outdoor workouts.

Learn how smoke and haze affect air quality, what AQI can tell you, and practical steps for cleaner indoor air, travel and N95 use.

Use today’s US AQI to make practical decisions about outdoor activity, children, commuting, windows, indoor air and particle respirators.

Understand reference monitors, low-cost sensors, satellite observations, atmospheric models and why air-quality readings can differ.

Compare US AQI, India’s National AQI and the European Air Quality Index without treating their numbers or colors as equivalent.

Understand why outdoor AQI is not an indoor reading, how pollution enters buildings and how sources, ventilation and filtration change exposure.

Learn how air-quality forecasts are produced, why current NowCasts and daily values differ, and what can make a forecast change.

Estimate US AQI sub-indices for PM2.5, PM10, ozone, carbon monoxide, nitrogen dioxide and sulfur dioxide.

Convert your city’s PM2.5 level into an equivalent number of cigarettes per day using the Berkeley Earth rule of thumb, and see what the comparison does and does not mean.

Estimate the PM2.5 dose you actually inhale across a day, adjusted for commute mode, hours outdoors, indoor filtration and mask use — rather than assuming you breathe the outdoor reading.

Estimate how many years of additional lung ageing long-term PM2.5 exposure may represent, based on your city, years lived there, and household and activity factors.

Estimate the annual productivity and health cost of breathing polluted air, based on your city’s PM2.5, your salary, job type, time outdoors and years of residence.

Learn what PM2.5 is, where fine particles come from, how they affect health, and the WHO guideline values for annual and daily exposure.

Learn what PM10 is, how it differs from PM2.5, common dust and combustion sources, health effects, and WHO guideline values.

Understand how ground-level ozone forms, why it differs from the protective ozone layer, its health effects and WHO guideline values.

Learn where nitrogen dioxide comes from, how it affects breathing, how it contributes to ozone and particles, and how NO₂ is used in AQI.

Understand sulfur dioxide sources, respiratory effects, particle formation and how SO₂ readings relate to air-quality indexes.

Learn why carbon monoxide is dangerous, common indoor and outdoor sources, warning symptoms and how CO is represented in AQI.

Reference the WHO 2021 guideline levels for PM2.5, PM10, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide.

Understand India’s National Ambient Air Quality Standards and CPCB AQI categories for PM2.5, PM10, ozone, gases and health communication.

Understand the EPA US AQI scale, its six health categories, pollutant breakpoints, dominant-pollutant method and current NowCast readings.

Learn how the European Air Quality Index uses six health bands, hourly pollutant concentrations, monitoring stations and modelled data.

A practical reference to construction dust sources, silica risks, wet methods, local exhaust and respiratory-protection limits.

Learn how cement dust affects eyes, skin and breathing, how silica can change the risk, and which controls reduce exposure.

Understand cotton and textile dust exposure, byssinosis, endotoxin concerns, ventilation and workplace respiratory protection.

Learn about respirable coal, silica and mineral dust, black lung and silicosis, and the controls used in mines and tunnels.

Understand what welding fumes contain, how metal and process change the risk, and why local exhaust is central to exposure control.

A sourced guide to respirable crystalline silica, silicosis, lung cancer risk, high-dust tasks and effective engineering controls.

Understand wood-dust sources, asthma and cancer risks, local exhaust ventilation, safe cleaning, exposure checks and RPE limitations.

Learn what N95 means, which particles it can filter, why fit matters, and where an N95 does not provide protection.

Understand the N99 rating, its filtration difference from N95, oil limitation, fit requirements and breathing-resistance tradeoffs.

Learn what the European FFP1 class means, its lower protection level, why fit testing matters, and when a higher class is needed.

Learn what the European FFP2 class means, how it differs from N95, why certification and fit matter, and what it cannot filter.

Understand the European FFP3 class, when higher particle protection may be selected, and the fit and hazard limits that still apply.

Learn what P100 means, its 99.97% minimum test efficiency, oil resistance, common formats and important limitations.

A guide to elastomeric half- and full-face respirators, particle filters, chemical cartridges, fit testing and maintenance.