Yes, it can be. If an air freshener hangs from your rear-view mirror and obstructs your view of the road, it’s considered a risk during an MOT. The Road Vehicles Regulations 1986 state that drivers must have an unobstructed view of the road and traffic ahead, so hanging fresheners that block your vision can cause a failure. We’ve seen this catch people out, especially with larger hanging fresheners or multiple items on the mirror. The simple fix is to remove any hanging items before your MOT and reattach them afterwards, or choose a different placement like the dashboard or air vents that doesn’t interfere with visibility.

Dealerships typically use professional-grade ozone treatments or chlorine dioxide gas for persistent smells. These aren’t standard air fresheners, they’re odour eliminators that chemically neutralise bad smells rather than masking them. The process usually involves sealing the car and running the treatment for several hours. From our experience, this level of treatment is only necessary for serious problems like smoke damage or mould. For everyday odours, dealerships clean the interior thoroughly first, replace cabin air filters, and then use scent diffusers or sprays. The key difference is they address the source before adding fragrance.

Keeping your car smelling fresh long-term comes down to regular cleaning rather than relying on fresheners alone. We’ve found that vacuuming carpets and seats weekly, wiping down surfaces, and keeping the cabin free of rubbish makes the biggest difference. Air fresheners just maintain what’s already clean. Replace your cabin air filter regularly, especially if you notice musty smells when the air conditioning runs. Drive with windows open occasionally to ventilate the cabin naturally. If you use air fresheners, one is usually enough, whether it’s a hanging type or a spray. Overusing fresheners creates a cloying smell that’s worse than none at all.

One is sufficient for most cars, regardless of size. Modern air fresheners are designed to disperse fragrance throughout the cabin, so adding more doesn’t improve the smell, it just makes it overpowering. We regularly see people complain about headaches or nausea from using multiple fresheners at once. If the scent isn’t strong enough with one freshener, the issue is usually that the car needs cleaning rather than more fragrance. A single passive freshener or a light spray before journeys gives a pleasant smell without overwhelming the space.

You can spray air freshener or disinfectant into the fresh air intake, usually located at the base of the windscreen under the bonnet. When the air conditioning runs, it’ll distribute the scent through the vents. Some people also attach scent pads to the cabin air filter itself, though we’d check the filter isn’t due for replacement first. Be careful with how much you spray. A light mist is enough, and overdoing it can leave residue in the ventilation system. If your air conditioning smells musty, cleaning the system with a proper disinfectant spray is more effective than just adding fragrance on top.

Bad smells need to be addressed at the source rather than covered up. For carpets and upholstery, a proper interior cleaner or upholstery shampoo removes the dirt and bacteria causing the smell. For persistent odours in the ventilation system, spray disinfectant into the air intake and run the air conditioning to distribute it. Replacing the cabin air filter often solves musty smells, especially if it's overdue. For serious issues like spilled milk or smoke damage, professional cleaning or ozone treatment might be necessary. Air fresheners won't fix bad smells, they'll just add fragrance on top of them, which usually makes things worse.