An air conditioner and filtering unit produces a positive or negative pressure to create an isolation space. A common air intake plenum has first and second inlets for admitting return air from the space or outside air which may be from a building main A/C system supply. Sanitized, cleaned and conditioned air is returned to the conditioned space; and condenser air is exhausted outside the conditioned space. The air intake plenum may be common to both the condenser air flow and to the evaporator air flow. A HEPA filter cleans the air suppled to both the condenser and the evaporator. A slide damper or other arrangement selectively opens and closes air flow through the first and second air inlets into the common intake plenum. This permits creation of overpressure, underpressure, or an intermediate pressure in the conditioned space. All air supplied to the room and all air exhausted from the room is cleaned and sanitized. The unit is self-contained and portable.