Colorcheck by Holmes Humidifier Replacement Filter HF206/HWF65 Only Holmes filters offer the benefit of baking soda and patented colorcheck. Arm & Hammer baking soda enhanced filter naturally deodorizes the air by absorbing and eliminating odors that come from garbage, bathrooms, pets, litter boxes, smoke and cooking. Colorcheck is a filter change indicator which turns color from purple to red as the filter needs replacing. For best results, change your filter as needed and clean your humidifier as directed by the manufacturer. 1 Filter Per Pack