What Is Ozone Treatment for Cars?

Ozone treatment for cars is a way of tackling odours by filling a closed, empty cabin with ozone gas from a portable generator. Ozone is a reactive form of oxygen that breaks down some smell-causing molecules by oxidising them. It reaches the air, vents and fabric surface, which is why it is often sold for smoke and pet smells. It has real limits, though: it does not lift the residue, hair or spills that most smells come from, and it irritates the lungs, so it has to be run carefully with nobody inside and the car aired properly afterwards.

What is ozone?

The Health and Safety Executive describes ozone as a form of oxygen: a colourless gas with a distinctive smell that occurs naturally in the atmosphere. Ordinary oxygen has two atoms; ozone has three, and that third atom makes it unstable and highly reactive. HSE guidance notes that ozone cannot be stored in containers because it breaks down spontaneously, so it is always generated where it is needed, by an electrical discharge or ultraviolet light. A car ozone machine is therefore a small generator that draws in air and turns some of its oxygen into ozone.

How is an ozone treatment carried out?

1. The car is cleaned first, ideally fully, so the gas is not trying to work against the source of the smell.
2. Everyone leaves the car, including pets, and anything not wanted in the treatment, such as child seats or clothing, is removed.
3. The generator is placed inside or fed through a slightly open window that is then sealed around the hose.
4. The ventilation is set to recirculate with the fan running, where the method allows, so ozone passes through the ducts.
5. The machine runs for a set time, usually from tens of minutes to a few hours depending on the smell and the generator.
6. The car is opened and aired thoroughly before anyone gets back in.

What can ozone do, and what can it not do?

Ozone can reduce some airborne odours and reach places a cloth cannot, such as inside the ducting. It is used in industry as an odour suppressant, according to HSE.

Its limits are significant. The US Environmental Protection Agency states that at concentrations that do not exceed public health standards, ozone is not effective at removing many odour-causing chemicals, and that contaminants embedded in porous materials may be unaffected. That matches what a valeter sees: if the smell is coming from tar film on a headliner, dog oil in a boot carpet or sick in seat foam, ozone does not take it out. It can also react with some chemicals to form irritating by-products. Ozone is at best a finishing step after the source has been removed.

Is ozone treatment safe?

Only with strict precautions. HSE says ozone's main health effect is irritation of the nose, throat and airways, with coughing and chest tightness, and that higher uncontrolled exposure can damage the lungs. The UK workplace exposure limit is 0.2 parts per million averaged over 15 minutes, which shows how little is needed to cause a problem. The EPA adds that the ability to smell ozone fades with exposure, so not smelling it does not mean the air is safe.

• Never sit in a car, or leave a pet or child in it, while a generator is running.
• Follow the machine's instructions on run time.
• Air the car with every door open for a good while afterwards, longer on cold, still days.
• People with asthma or lung conditions should take extra care, as ozone can aggravate allergies and asthma; see a GP if you notice symptoms.

Can ozone damage a car interior?

It can with heavy or repeated use. HSE notes that low concentrations of ozone affect textiles, fabrics, dyes, plastics and paints, and cause the cracking of stressed rubber. In a car, that means door seals, wiper rubbers, elastic in seat covers and some plastics could age faster if a cabin is treated often or for very long periods. An occasional, correctly timed treatment is unlikely to cause visible harm, but it is a reason not to treat ozone as routine maintenance.

What is the alternative for stubborn smells?

Remove the source. Most persistent car odours come from residue in fabric, the headliner and the cabin filter, which is why we deal with odours through cleaning rather than gas. We do not offer ozone treatment; odour work is part of our steam cleaning service, which lifts residue out of seats, carpets and vents, from £60, and our mould removal treatment for musty cars, from £80. For a side-by-side look at which approach suits which smell, read steam cleaning versus ozone for car odours, and for smokers' cars specifically, see how to get rid of cigarette smell.

Sources

• HSE: Ozone: health hazards and control measures (EH38)
• US EPA: Ozone generators that are sold as air cleaners