Make sure the model you choose will take out the pollutants that concern you and check that replacement filters are readily available.

A gauge indicates when it is worn out, and a replacement filter is $112.

The bottle is about $8 at housewares stores, and replacement filters are about $3.50.

He said that it had been two years since he used it and that he had no idea where to obtain replacement filters.

The magazine continued to report that contaminated replacement filters were still being sold, but no Government agency ever notified the public because none of them halted the sale of the filters.

The Kenmore 75121 has a permanent filter that will need to be cleaned periodically, but because it is re-usable, you will not have the extra expense of buying replacement filters.

Appliance stores sell both washable and nonwashable replacement filters.

Prices range from about $20 to $500 and replacement filters can add up to $25 to $150 a year.

The full system has a list price of $49.95, and a replacement filter, $19.95.

Since the Comfort Air market consists mainly of replacement filters, operations in this segment are relatively insensitive to fluctuations in the economy.