The Allerair 5000 DS air purifiers feature a unique tar-trapping pre-filter that grabs larger particles and tar which also extends the life of the HEPA filter and carbon filter. The unit also features a micro-wrap filter to deal with small particles as small as the fine cigarette ash and a 3 in. extra-deep 22 lb carbon filter which increases dwell time allowing more chemicals gases and odors to be absorbed. An even deeper 3.5 in. with 28 lb carbon filter is available with the DXS model. The only proven to work method of adsorbing lingering substances that result from tobacco smoke in a closed environment even when active smoking has ceased.