HVAC design encompasses a comprehensive process beyond simple load calculations and equipment selection. It involves understanding the specific characteristics of the space being served, as well as considering the type of occupancy and the relevant codes and regulations that govern it. Good engineering practices and published data offer more questions than answers until the building requirements are broken down into what is relevant for proper design, ventilation rates and temperature control aspects.
The primary objective of HVAC design has remained consistent over time: to efficiently create safe and comfortable indoor environments. However, this process is continuously evolving and faces challenges such as meeting building codes, ensuring energy efficiency of equipment and system operation, and prioritizing occupant comfort, ventilation, and air quality.
When it comes to hospital air conditioning, it is a highly critical aspect in coordination with other services. A recently completed healthcare project by NAIPL involved the construction of a multi-specialty hospital. Two key considerations were the implementation of a high-end HVAC system tailored for healthcare facilities and the challenge of working within the height restrictions between the false ceiling and the slab to accommodate all necessary services. Additionally, navigating the ducts and pipes within the beams posed another significant challenge. The project aimed to incorporate all modern facilities available in renowned hospitals like Apollo or Yashoda, despite the construction area spanning nearly 20,000 square feet.
Various aspects need to be discussed in the planning stage itself, which will help in smooth execution.
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- Maintaining precise air control within and between rooms is crucial, particularly during medical procedures. Even small air locks of 20 square feet have been carefully designed to create a positive pressure difference from neighboring rooms, achieved by regulating fresh air flow.
- To ensure a clean and healthy environment, specific ventilation and filtration systems have been implemented to effectively dilute and remove airborne microorganisms, viruses, and unpleasant odors. Each room is equipped with separate fans and individual ducting to prevent air from mixing.
- Different areas within the facility have unique temperature and humidity requirements, which couldn’t be adequately addressed by a standard VRV system. As a result, specialized dehumidifiers have been strategically placed in different rooms to maintain optimal humidity levels.
- The environmental conditions are meticulously controlled by a centralized VRV system, while air quality and movement are managed through air handling units, fan coil units, and Treated Fresh Air units.
- The design of the hospital rooms prioritizes creating a welcoming and comfortable atmosphere, especially for high-end clients who may be waiting for their appointments. The design team has dedicated significant effort to making various alterations to achieve this goal while upholding their technical responsibilities as consultants.
Control of infection sources and its measures in Operation Rooms
Infectious bacteria can be carried through the air, posing a risk of spreading diseases. Tiny droplets or infectious agents that are 5 micrometers or smaller have the ability to remain suspended in the air for extended periods of time. Studies have demonstrated that filters with an effectiveness of 90 to 95 percent can eliminate 99.9 percent of bacteria in hospital environments. Epidemiological evidence and other research suggest that many of the airborne viruses responsible for transmitting infections are extremely small in size. As a result, there is currently no known method to entirely eradicate 100 percent of viable particles. HEPA filters or Ultra-Low Penetration (ULPA) filters are the most efficient options available for removing these microscopic threats. To combat the spread of airborne viruses in hospitals, isolation rooms with appropriate ventilation pressure relationships are employed as a preventive measure.
Use of Treated Fresh Air system in entire premises
Fresh air, also known as Treated Fresh Air (TFA), is essential for maintaining a healthy environment in hospitals. Unlike room air, outdoor air is significantly lower in bacteria and viruses. In hospitals, many infection control issues arise from the presence of bacteria and viruses within the facility. Ventilation systems play a critical role in reducing the spread of these contaminants by diluting them in the air. Additionally, well-designed and properly maintained ventilation systems help to maintain the correct pressure relationships between different areas and eliminate airborne infectious agents from the hospital environment. To ensure a continuous air change in the premises, each room is supplied with fresh air at a rate of 15 CFM per person, while the same amount of air is continuously extracted through toilet fans.
Isolation Rooms( NICU)
In order to prevent the spread of contagious microorganisms and control infections, it is essential to have a dedicated NICU room that is separated from other areas. This room should include the following special isolation facilities:
1. Standard Pressure Room: This room is designed for patients who require contact or droplet isolation.
2. Negative Pressure Room: This room is intended for patients who require airborne droplet nuclei isolation to reduce disease transmission via the airborne route (Class-N).
3. Separate Exhaust System: The NICU room needs a dedicated exhaust system that removes a greater quantity of air than the supply system provides.
4. Direct Exhaust to Outside: The exhaust from the NICU room should be directed outside and include a bypass connection.
5. Positive Pressure Room: This room should be equipped with a positive pressure relative to the ambient pressure to isolate immunocompromised patients, such as certain transplant and oncology patients.
Humidity Control
Bacteriological microorganisms can hitch a ride on dust particles, especially when the air is dry, as they are more likely to be attracted to each other due to increased static energy. In hospitals, high humidity can create an environment conducive to the growth of Pseudomonas aeruginosa, a dangerous bacterium. Conversely, in operating rooms, maintaining an optimal level of humidity is believed to help prevent dehydration of exposed tissue. When the relative humidity is around 50%, a nearly imperceptible film of moisture forms on equipment and surfaces, which helps to dissipate static electricity and reduce the risk of sparks. To minimize the risk of explosions, it is recommended to maintain a relative humidity level between 40% and 65%. Additionally, VRV Indoor Units come equipped with humidity indicators in the remote controls and a few portable time dehumidifiers have been provided for added control.
Conclusion
The entire design team has diligently focused on addressing every small detail, with the invaluable support of a team of doctors. Their goal is to maximize the provision of facilities within the confines of limited space.