An operation theatre must have clean air during surgeries like orthopaedic surgery to avoid infection of the wound, which may prove fatal in certain cases, involving lots of legal complication these days. To keep the air clean of dust, fungus, micro organisms, filtration is the only system available. The HEPA (High Efficiency Particulate Absolute) filter, the filtration of air on control velocity condition, can provide cleanliness of air as defined in the federal Standard 209 E. The system as a whole is known as laminar flow system. For clean air in the O.T. vertical air flow unit with HEPA filter and two suction units with pre-filters are placed at the bottom of two opposite walls of the room, the system can be tailor made as per customer's requirements. Working principle: atmospheric air suction through 5 micron filter and pass through HEPA filter on controlled velocity and provide sterile air. Working principle for OT room: the pre-filtered units are placed in suction point on two opposite walls of OT. The pre-filters have adjustable speed blowers with over temperature protection. The OT air is sucked from the bottom via pre-filters and sent back through vertical chamber (with HEPA filters) placed exactly over the operation table. The efficiency of HEPA filters is 99.999% of all particles larger than 0.3 micron. The velocity of air at outlet is 0.45 m/s, which provides bio-clean air as per Federal Standard 209 E. The control box contains normal, start, stop & speed control for blowers. Supervision panel with individual LED indicator for each blower showing their status and an alarm circuit for emergency. Air movement: the air flow is vertical from the filter ceiling over the operating table to the suction units placed at the bottom of two opposite walls of the operating theatre. The vertical flow from ceiling units divided over the operation area of both the side depending on the customer's requirement. Effective working areas can be adjusted through ceiling unit design. The air circulation will be 120 to 400 times depending on OT room size. This Laminar air flow is ultra cleaned over the entire operating area and instantly the theatre is bacteria free. Blower and motor: the unique super silent centrifugal blower with integral motor is statically and dynamically balanced to extremely close limits. All moving balanced to extremely close limits. All moving parts are isolated from the casing by efficient anti-vibration mountings. The no speed pulsation, totally sealed, continuous duty motor with built-in overload protection is factory lifetime lubricated and needs no service. Electric speed control, due to a havened speed performance curve, the blower gives almost automatic speed compensation for rising air resistance as the static pressure across the HEPA – filter builds up to its maximum dust loading capacity.