Do you get what you pay for in a furnace filter?

Basic fibreglass filters ($1 to $5) trap large particles (about 10 per cent of dust) and not much more. Change every month.

Pleated-media filters ($10 to $15) trap some allergens and about 40 per cent of airborne particles. Change every two months.

Electrostatically charged filters ($15 to $30) trap 30 times more allergens and particles than basic filters and can trap smoke particles. Change every three months.

Washable filters ($30 to $50) also feature electrostatic material and trap a variety of larger particles (although not as efficiently as their disposable counterparts). Wash every 30 days with warm water and change every five years.