Abstract: The present invention relates to a respiratory protective apparatus utilizing a powered filtering device having a housing, with at least one inlet and an outlet, and a pump located between the inlet and the outlet for pumping air therebetween. The powered filtering device has a controller, preferably located at or near the outlet of the housing, for adjusting the air flow between the inlet and the outlet in response to a wearer's breathing pattern. Preferably, the controller does this by predicting the future breathing pattern of the wearer based on the past breathing pattern of the wearer. The powered filtering device also has a monitor to determine if the air flow through the respiratory protective apparatus falls below a set level and it does, alert the wearer to this condition.