Whirlpool filters should be replaced whenever the filter change indicator is illuminated. Not all models, though, offer this feature. As a rule of thumb, your Whirlpool prefilters should be replaced every 3 months. This ensures the filter can continue to remove odors and smoke from your home. Whirlpool HEPA filters should be replaced annually for each machine. Replacing your Whirlpool filter is an easy and inexpensive way to keep your Whirlpool air purifier performing its best while maintaining cleaner air inside your home.