Holmes has discontinued the HAPF38 HEPA Filter and lists the Holmes HAPF-38 HEPA Air Filter Replacement as a replacement.
The Holmes HAPF38CS HEPA Filter, which fits Holmes air purifier model HAP292 (HAP-292), removes airborne allergens and reduces unwanted smells and odors by capturing fine particulates that float in the air. This genuine Holmes HEPA filter replaces the HAPF-38 and is also known as H38 and HAPF38. It should be used with the Holmes HAPF92CS Carbon Odor Pre-Filter.
You should replace your HEPA filter at least every 12 months for optimum performance.