Portable interior filters are powered by plugging into the car cigarette lighter. They draw the air inside the car through a filter medium inside them – either fabric, activated charcoal or an electrostatic surface which attracts particles – or some combination of these. For full effectiveness, keep windows closed.
The benefits of this type of filter compared to the air intake filters are that they are portable, and you can use them in any car or vehicle in which you travel. They also filter the air inside the car -so they can take out particles such as moulds, dust mites, pet hairs, and fumes from plastics, foams and materials in the car. Their main disadvantage is that unless you have a car with a recirculating air system (see page 427), they are much less effective when you use the ventilating or heating system because of fumes entering from outside. They are best used without operating air vents or heating.
One model – the NSA 600A Auto Air System – has only just been introduced in the UK and there are no reports from users of its effectiveness. It has an electrostatic filter, fabric filters and a thin activated carbon filter to absorb chemical vapours. It has an optional fragrancer which you should not use if you are chemically sensitive. It is close to 30 cm (1 foot) high and has a Velcro mounting to hold it to a surface. Its price is quoted at £110 (at 1992): replacement filters will be required regularly, depending on how much you drive. Contact NSA for names of distributors; ask for a trial period (address below).
Another portable car filter is available for import direct from the United States. The Foust #160A Air Purifier is a free-standing cylinder resting horizontally on a small bracket, about 40 cm (16 inches) in length and 23 cm (9 inches) in height. Made of metal, it contains filter media of activated carbon, alumina with potassium permanganate and a particle filter. If you think you might be sensitive to any filter media, you can obtain test samples in advance of buying a filter and Foust will supply cartridges with different types of filter mix to your needs. The Foust purifier is very effective against chemical fumes. It can be noisy, and get in the way if you have a full car load of people.
The purifier costs $242. Replacement charcoal, needed every six to twelve months, costs $18. The Test Kit costs $19. To these prices, you will need to add shipping charges, plus duty and
VAT, to be paid when the parcel arrives in this country. Duty at 4.25 per cent and VAT at 17.5 per cent will mean adding £28 to the filter, £2.20 to the cartridge, and £2.60 to the Test Kit. Shipping charges are quoted separately by Foust at time of order.