We advise that our filters last 3 months of use or until the filters become clogged* or damaged (whichever point is reached sooner). This is based on HSE guidance** and is assuming that the user is breathing through the filters for an average of 40 hours per week, 8 hours per day plus that the filters are well-maintained. Filter longevity is also subject to an individual’s breathing rate and the level of contamination present in the work environment. * The definition of a 'clogged' filter is when it becomes difficult for the user to breathe through it. ** HSG53/COSHH essentials R3