WCAS/monitoring/O3
Ozone (O3) is both a natural component of the atmosphere and a major constituent of photochemical smog. At normal atmospheric concentrations it is an odourless, colorless gas. However, at concentrations higher than one ppm, such as found near photocopier machines and near electrical discharges, it has a sharp odour.
Ozone is a strong oxidizer and can irritate eyes, nose and throat and decrease athletic performance. High concentrations can increase susceptibility to respiratory disease and reduce crop yields.
Unlike other pollutants, ozone is not emitted directly into the atmosphere but is produced through a series of chemical reactions in the atmosphere. Concentrations are controlled mainly by emissions of nitrogen oxides and reactive hydrocarbons. Ozone is a natural component of the upper atmosphere and may be transported to ground level by meteorological processes.
Alberta Environment guidelines for ozone are:
| Concentration (ppb) | Exposure Time | Human Symptoms and Other Effects |
| 10,000 | — | Severe pulmonary edema; possible acute bronchiolitis; decreased blood pressure; rapid weak pulse |
| 1,000 | — | Coughing; extreme fatigue; lack of coordination; increased airway resistance; decreased forced expiratory volume |
| 500 | — | Chest constriction; impaired carbon monoxide diffusions capacity; decrease in lung function without exercise |
| 300 | — | Headache; chest discomfort sufficient to prevent completion of exercise; decrease in lung function in exercising subjects |
| 250 | — | Increase in incidence and severity of asthma attacks; moderate eye irritation |
| 150 | — | For sensitive individuals, reduction in pulmonary lung function; chest discomfort; irritation of the respiratory tract, coughing and wheezing |
| 150 | — | Threshold for injury to vegetation |
| 120 | — | US national primary and secondary ambient air quality standard |
| 100 | — | Maximum allowed by OSHA in industrial work areas |
| 82 | 1 hour | Alberta ambient air quality guideline |
| 50 | — | Maximum recommended by ASHRAE in an air conditioned and ventilated space |
| 20–40 | — | Range in which ozone occurs in healthy outdoor environments. Also ozone level produced by some indoor air ionizers when operated according to instructions. |
| 25 | 24 hour | Alberta ambient air quality guideline |
| 3–10 | — | Low range at which average person can smell ozone |
| 1 | — | Most indoor environments — windows open |