Many manufacturers will include multiple stages of filtration in their product. For example, there may be a stage 1 prefilter with an activated carbon component. This pre filter will reduce odors and VOCs – and extend the life of the main HEPA filter by capturing very large particles. If the prefilter does not include activated carbon – another stage 3 filter with carbon may be present. Some manufacturers will include all 3 stages in 1 filter.