A modular powered air purifying respirator (PAPR) is provided including one or more of a first inlet configured to receive an ambient gas; a gas filter in fluid communication with the first inlet and configured to filter the ambient gas; a blower configured to boost at least one of a flow rate or a pressure of the ambient gas entering and/or exiting the gas filter; a second and independent inlet configured to receive a non-ambient gas; a first outlet configured to selectively provide a breathing gas to a user from the ambient gas or the non-ambient gas; and/or a controller and switching device configured to select the source of the breathing gas between the first inlet and the second inlet. Embodiments may also include a power source for the blower.