A makeup air unit comprising a housing defining a compartment. The housing further defines at least one exhaust inlet for receiving air from an indoor space into the compartment and at least one exhaust outlet for passing air from the compartment to the atmosphere. The housing further defines at least one intake inlet and at least one intake outlet each extending into the compartment. The exhaust inlet and outlet are fluidly disconnected from the intake inlet and outlet. An air moving device overlies the intake outlet and is configured to transfer air from the compartment through the intake outlet into the work space. A flap switch unit is disposed in the compartment adjacent to the exhaust outlet and is configured to detect a flow of air through the exhaust inlet and to activate the air moving device in response to a detection of the flow of air.