Indoor air cleaning systems may help to reduce levels of allergens and pollutants in indoor air to create a cleaner, healthier work and home environment. There are a number of different types of air cleaners and filtration systems; HEPA, ULPA, carbon filter, electrostatic, electret, negative-ionizing, UV, and ozone generators. It's important to know the air cleaning needs for the situation when selecting an appropriate system. A word of caution is needed when choosing an air purifier. These are less effective in large areas and need to be designed for specific irritants. For example, certain air purifiers will not work for fragrances but will work for smoke. It's important to work with a vendor to make certain of what can be effective for the situation.