Air Change Per Hour:
Minimum total air changes should be 25 based on international guidelines although the same will vary with
biological load and the location.
The fresh air component of the air change required to be a minimum of 4 air changes out of a total minimum of 25 air changes.
Air Velocity: The vertical downflow of air coming out of the diffusers should be able to carry bacteria carrying particle load away from the operating table. The airflow needs to be unidirectional and downwards on the OT table.
Positive Pressure: There is a requirement to maintain a positive pressure differential between OT and adjoining areas to prevent outside air entry into OT. The minimum positive pressure recommended is 15 Pascal (0.05 inches of water) as per ISO 14644 Clean Room Standard.
Air handling in the OT including Air Quantity:
Air supplied through HEPA filters in the AHU. The minimum size of the air supply area should be 6’ x 4’ to cover the entire OT table and surgical team The minimum supply air volume to the OT (in CFM) should be compliant with the desired minimum air change. The Air exchange from the exhaust grille located near the floor level (approx. 6 inches above the floor level).
The air quality at the supply i.e. at grille level Class 1000/ ISO Class 6 (at rest condition). Class 1000 means a cubic foot of air must have no more than 1000 particles measuring 0.5 microns or larger.
Temperature and Humidity:
The temperature should be maintained at 21 +/- 3 Deg C inside the OT all the time with corresponding relative humidity between 40 to 60% though the ideal Rh is considered to be 55%. Appropriate devices to monitor and display these conditions inside the OT may be installed.
Air Filtration: The AHU must be an air purification unit and air filtration unit. There must be two sets of washable flange type pre-filters of capacity 10 microns and 5 microns with aluminum/ SS 304 frame within the AHU. The necessary service panels to be provided for servicing the filters, motors & blowers. HEPA filters of efficiency 99.97% down to o.3 microns or higher efficiency may be provided in the AHU.
The AHU of each OT dedicated and not linked to the air conditioning of any other area.
During the non-functional hours, the AHU blower will be operational round the clock (maybe without temperature control).
VFD devices may be used to conserve energy.
Window & split A/c should not be used in any type of OT because they are pure recirculating units and have convenient pockets for microbial growth which cannot be sealed.
The flooring, walls, and ceiling should be non-porous, smooth, seamless without corners, and should be easily cleanable repeatedly.
Validation of system to do as per ISO 14664 standards and to necessarily include:
Air particulate count
Temperature and Humidity check
Air Change Rate Calculation
Air velocity at the outlet of terminal filtration unit /filters
Pressure Differential levels of the OT ambient/adjoining areas
Validation of HEPA Filters by appropriate tests like DOP etc.
Maintenance of the system: Recommended that periodic preventive maintenance carried out in terms of cleaning pre-filters at the interval of 15 days. Preventive maintenance of all the parts carried out as per manufacturer recommendations.
