A powered air purifying respirator (PAPR) module comprising: a housing having a central axis and formed by an upper cylindrical portion and a lower cylindrical portion ; a fan mounted in the lower cylindrical portion , a motor mounted in the housing and operably connected to the fan for driving the fan , and at least one battery mounted within the housing and operably connected to the motor for powering the motor ; an inlet defined by an internal sleeve in the upper cylindrical portion in fluid communication with the fan and configured to selectively receive a filter canister for filtering air that is drawn into the inlet ; and an outlet defined by an external sleeve in the lower cylindrical portion and in fluid communication with the fan ; characterized in that : a lower body cover in the lower cylindrical portion seals a breathing zone in the lower cylindrical portion from an enclosed space in the upper cylindrical portion ; the at least one battery is mounted in the enclosed space in the upper cylindrical portion ; the fan and motor are in the sealed breathing zone , which is in fluid communication with the inlet and the outlet , wherein the inlet and the outlet are coaxially aligned, and wherein the outlet is adapted to mount the housing to a facepiece of a respirator mask or to a conduit that is fluidly connected to a facepiece inlet opening in a respirator mask; whereby the modular PAPR can be positioned between a filter canister and a respirator mask or between a filter canister and a conduit that is connected to a respirator mask. a housing having a central axis and formed by an upper cylindrical portion and a lower cylindrical portion ; a fan mounted in the lower cylindrical portion , a motor mounted in the housing and operably connected to the fan for driving the fan , and at least one battery mounted within the housing and operably connected to the motor for powering the motor ; an inlet defined by an internal sleeve in the upper cylindrical portion in fluid communication with the fan and configured to selectively receive a filter canister for filtering air that is drawn into the inlet ; and an outlet defined by an external sleeve in the lower cylindrical portion and in fluid communication with the fan ; characterized in that : a lower body cover in the lower cylindrical portion seals a breathing zone in the lower cylindrical portion from an enclosed space in the upper cylindrical portion ; the at least one battery is mounted in the enclosed space in the upper cylindrical portion ; the fan and motor are in the sealed breathing zone , which is in fluid communication with the inlet and the outlet , wherein the inlet and the outlet are coaxially aligned, and wherein the outlet is adapted to mount the housing to a facepiece of a respirator mask or to a conduit that is fluidly connected to a facepiece inlet opening in a respirator mask; whereby the modular PAPR can be positioned between a filter canister and a respirator mask or between a filter canister and a conduit that is connected to a respirator mask. a lower body cover in the lower cylindrical portion seals a breathing zone in the lower cylindrical portion from an enclosed space in the upper cylindrical portion ; the at least one battery is mounted in the enclosed space in the upper cylindrical portion ; the fan and motor are in the sealed breathing zone , which is in fluid communication with the inlet and the outlet , wherein the inlet and the outlet are coaxially aligned, and wherein the outlet is adapted to mount the housing to a facepiece of a respirator mask or to a conduit that is fluidly connected to a facepiece inlet opening in a respirator mask; whereby the modular PAPR can be positioned between a filter canister and a respirator mask or between a filter canister and a conduit that is connected to a respirator mask. <EOS>