# Article: Cleanroom HVAC System Design for Hospital Operating Theatres

## Brief Introduction
As the core for airborne cleanliness control in clean operating rooms, the clean air conditioning system features high technical requirements, stringent quality standards for construction and installa

## Main Content


As the core for airborne cleanliness control in clean operating rooms, the clean air conditioning system features high technical requirements, stringent quality standards for construction and installation, and relatively large capital investment. Failure to meet operational specifications will result in substantial losses.



To assist industry peers in understanding and proficiently mastering the design of air conditioning systems for clean operating rooms, we share key design points herein to avoid common technical errors during construction.

1. Layout Requirements for Air Conditioning and Exhaust Systems

The purified air conditioning system shall keep the clean operating department under effective control, enabling both overall regional management and flexible independent operation of each individual clean operating room.

Separate purified air conditioning systems shall be installed for clean operating rooms and auxiliary rooms.

Class I and Class II clean operating rooms shall be equipped with an independent purified air conditioning system for each room. For Class III and Class IV clean operating rooms, independent single-room systems are preferred; alternatively, 2 to 3 operating rooms can share one purified air conditioning system.

Independent purified air conditioning systems shall be adopted for clean auxiliary areas and clean utility auxiliary areas respectively. For large-scale operating departments, zoned system layout is recommended for easier operation and management.

The clean operating department shall be supplied with sufficient outdoor fresh air volume, with reliable measures to guarantee stable fresh air supply to each operating room.

A dedicated exhaust system shall be installed for every single operating room. Exhaust outlets shall be reserved in clean auxiliary and utility auxiliary zones to maintain a reasonable pressure gradient across the entire operating department.

The cold and heat source of the operating department shall be designed to satisfy simultaneous cooling and heating demands of the whole clean operating department.

Reliable regulating devices shall be fitted on all purified air conditioning and exhaust systems to limit the volume deviation of supply air, return air, fresh air and exhaust air within allowable tolerance.

2. Air Treatment Methods

Recirculated air of the purified air conditioning system shall pass through three-stage filtration: the first-stage filter is installed close to return air inlets, the second-stage filter is located in the positive-pressure section of the ductwork, and the third-stage filter is mounted at the terminal end of the system.

The purified air conditioning system shall conduct thermal and humidification/dehumidification treatment on supply air in accordance with the grade requirements of operating rooms.

3. Air Distribution Organization

Clean operating rooms adopt top supply and bottom return airflow pattern. For clean auxiliary and utility auxiliary rooms, top supply & bottom return is recommended, while top supply & top return is also acceptable.

Air supply outlets of Class I ~ III clean operating rooms shall be centrally arranged right above the operating table, ensuring the surgical area is covered by the main clean airflow zone.

Clean operating rooms shall adopt bottom return air on both sides; single-side bottom return is permitted if the distance between two side walls is no more than 3 meters.

The top edge of bottom return air grilles shall not exceed 0.5 m above finished floor level, and the bottom edge shall be no less than 0.1 m above the floor.

Return air grilles in Class I operating rooms shall be arranged in a continuous full-length strip.

Air velocity at indoor return air grilles ≤ 1.6 m/s; air velocity at corridor return air grilles ≤ 3 m/s.

A ceiling exhaust outlet shall be installed in clean operating rooms, preferably above the patient’s head side on the ceiling, with exhaust air velocity no more than 2 m/s.