Abstract: A method of controlling a powered air purifying respirator blower system to deliver a substantially uniform volumetric airflow to a user includes the steps of determining one of (a) ambient air density or (b) ambient air temperature and ambient air pressure, and adjusting an electrical characteristic of the electric motor in response to the determination and the at least two calibration values. The powered air purifying respirator blower system may include a fan powered by an electric motor, the motor being controlled by an electronic control unit for delivering a forced flow of filtered air to a user. In some embodiments, the electronic control unit may be operable to adjust an electrical characteristic of the motor in accordance with a predetermined correlation between the speed of the fan and the applied motor electrical characteristic for a selected substantially uniform volumetric airflow from the fan.

Abstract: A method of controlling a powered air purifying respirator blower system to deliver a substantially uniform volumetric airflow to a user (6) includes the steps of determining one of (a) ambient air density or (b) ambient air temperature and ambient air pressure, and adjusting an electrical characteristic of the electric motor (22) in response to said determination and said at least two calibration values. The powered air purifying respirator blower system may include a fan (21) powered by an electric motor (22), the motor being controlled by an electronic control unit (23) for delivering a forced flow of filtered air to a user (06). The electronic control unit (23) may include at least two calibration values for the electrical characteristics of the electric motor (22) stored therein. The system may include at least one sensor (26) adapted to be in communication with the electronic control unit and arranged to determine one of (a) ambient air density or (b) ambient air temperature and ambient air pressure.