HEPA filters. HEPA is an acronym that stands for high-efficiency particulate air. HEPA air purifiers and vent filters can reduce airborne pet allergens. HEPA filters are made of fiberglass filaments with very small diameters. They are designed to target and trap microscopic particles and pollutants. HEPA filters work by mechanical means that reduce the side effects of asthma and allergies. These air-purifying filters remove 99.97 percent or more of allergy-causing particles. They need to be replaced every two to three years to work properly. Some vacuum cleaners incorporate HEPA filters into their filtration systems. They are extremely useful for removing pet allergens that become trapped in upholstery and rugs.