There was an accompanying paper that went into some detail on mould contamination from air conditioning units in the house and car which generally supported the advice given above. It also mentioned that antifungals are being applied to some new air con filters which might account for some of their efficiency at removing mould spores from the air, but this seemed to have a useful life of 2 years.
Another research paper has just been published on this subject and once again it has been shown that the air conditioning filtration material can provide a good environment for moulds to grow in if left with no airflow - so it is recommended not to leave the unit switched off.
However they also showed that once switched on a clean set of filters can be very effective - the number of spores in the air drops 75% within 10 minutes which is a very similar result to the earlier paper.
Guidelines to avoid mould buildup in your car air conditioning
- Keep it switched on
- Ensure it is maintained regularly
- Ensure the filtration material is renewed regularly
- If you haven't used your car for a week or more run the air conditioning at full airflow setting for 10 mins before getting into the car