3M Filtrete 9803DC-6 Air Cleaner Filter Instructions:
Replace the filter every 3 months.
Certain conditions in your home will significantly add particles to the air. This will cause the filter to capture more particles than usual, shortening it's life to less than three months or reducing the effectiveness of the filter to capture particles. These conditions include: tobacco smoke, sanding projects, pets, woodburning fireplaces, construction work, burning candles, dirty ductwork, etc.