What is ozone?
Ozone is a naturally occurring gas composed of three oxygen atoms. When most people think of ozone (O3), they picture a thin layer of gas high above the earth’s outermost atmosphere that protects the earth from the sun’s ultraviolet rays. But ozone, often described as the ‘fresh smell’ after a thunderstorm, has a variety of uses closer to home.
Ozone was first discovered in 1840 and has been used as a disinfectant in drinking water since 1893. In comparison to chlorine, the most common water disinfection chemical, ozone is a stronger oxidiser and acts over 3,000 times faster than chlorine.
Ozone is generated via a number of processes such as electrical discharge or UV radiation. It is either produced intentionally for use during a specific process or as a byproduct of a process, for example during photocopying. Due to its reactivity ozone rapidly decomposes back to oxygen and is extremely difficult to store. It is normally generated on site.
Ozone has been safely produced industrially in a variety of applications for a number of years. Uses include improving air quality in offices, odour suppressers in hotel rooms, commercial kitchens, food processing, disinfectant in drinking water production, swimming pools and in laundry.
It is present in the air we breath at a typical concentration of 0.001 to 0.05ppm and is detectable at very low concentrations. The human nose can detect ozone at concentrations as low as 0.01ppm. Generally a concentration of 0.02ppm is regarded as the worldwide background level. In London during the summer ozone averages between 0.04 and 0.06ppm, but on smoggy days this may increase to 0.2ppm for some hours.
The Health & Safety Executive (HSE) recommended Workplace Exposure Limit (WEL) for ozone is 0.2ppm (0.4mg/m3). Taking into consideration the available human toxicity data, the HSE has concluded that no significant effects on health would be expected to occur in normal workplace activities from exposure to 0.2ppm ozone for up to 7 hours.