Modular Operation Theatre
The Revised Guidelines for Air-Conditioning System for Operation Theatres
A. The air conditioning requirements for Operation Theater in an HCO have been deliberated at length with manufacturers, engineers, technical cornmittee members and other stake holders and the following guidelines have been finalised.
B. For this purpose operation theaters have been divided into two distinct groups:
i. Superspeciality OT: Superspeciality OT means operations of Neurosciences, Orthopedics (Joint Replacement), Cardiothoracic and Transplant Surgery (Renal, Liver etc).
ii. General OT: This includes Ophthalmology and all other basic surgical disciplines. District hospital OTs and FRU OT would fall under this category.
C. The following basic assumptions have been kept in view:
• OT Size: Standard OT size of 20' x 20' x 10' (Ht. below the false ceiling level is considered).
• Occupancy: Standard occupancy of 5-8 persons at any given point of time inside the OT is considered.
• Equipment Load: Standard equipment load of 5-7 kW considered per OT.
• Ambient temperature & humidity at each location to be considered while designing the system.
1. REQUIREMENTS — Super - Specialty OT
I. Air Changes Per Hour:
• Minimum total air changes should be 30 based on international guidelines although the same will vary with biological load and the location.
• The fresh air component of the air change is required to be minimum 5 air changes out of total minimum 30 air changes.
• If HCO chooses to have 100% fresh air system than appropriate energy saving devices like Heat Recovery Wheel, Run around Pipes etc should be installed.
II. Air Velocity: The vertical down flow 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. The air velocity recommended as per the international and national guidelines is 90-120 FPM at the Grille/ Diffuser level
III. Positive Pressure: There is a requirement to maintain 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.
IV. Air handling in the OT including air Quality: Air is supplied through Terminal HEPA filters in the ceiling. The minimum size of the filtration area should be 8' x 6' 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 return air should be picked up/ taken out from the exhaust grille located near the floor level (appx 6 inches above the floor level). The air quality at the supply i.e. at grille level should be Class 100/ ISO Class 5 (at rest condition). Class 100 means a cubic foot of air must have no more than 100 particles measuring 0.5 microns or larger.
V. 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.
VI. 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 are to be provided in the OT and not in the AHU.
2. REQUIREMENTS — General OT
I. 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 is required to be minimum 4 air changes out of total minimum 25 air changes.
II. Air Velocity: The vertical down flow 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.
III. Positive Pressure: There is a requirement to maintain 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.
IV. Air handling in the OT including Air Quantity: Air is 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 return air should be picked up/ taken out 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 should be 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.
V. 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.
VI. 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.
3. General Guiding Notes:
• The AHU of each OT should be dedicated one and should not be linked to air conditioning of any other area.
• During the non functional hours AHU blower will be operational round the clock (may be 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 re circulating 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. The material should be chosen accordingly.
• Validation of system to be done as per ISO 14664 standards and to be necessarily include:
¤ Temperature and Humidity check
¤ Air particulate count
¤ Air Change Rate Calculation
¤ Air velocity at outlet of terminal filtration unit / filters
¤ Pressure Differential levels of the OT wrt ambient / adjoining areas
¤ Validation of HEPA Filters by appropriate tests like DOP etc.
• Maintenance of the system: It is recommended that periodic preventive maintenance be carried out in terms of cleaning of pre filters at the interval of 15 days. Preventive maintenance of all the parts is carried out as per manufacturer recommendations.
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