5 Hospital HVAC Design Strategies for the Post-COVID-19 World
Many of the interventions made by the A/E/C sector to assist hospitals in responding with temporary retrofit solutions to meet the surge demands of the COVID-19 pandemic were concentrated on enhancing or modifying existing HVAC systems to produce negative pressure in a typical medical/surgical patient room.
The best techniques from the retrofits must be used in ongoing initiatives as well as in the planning and construction of new hospitals.
Hospitals will need to think about investing in hospital HVAC systems with the right components and infrastructure to offer the atmosphere needed to enable acuity adaptive isolation areas for viruses like COVID-19, or other airborne infections.
The five factors and potential methods for constructing a reliable HVAC system that can accommodate future flexibility are listed below.
1. HEPA Filtration Recommendations
HEPA particle filtering should be properly implemented and maintained in hospital HVAC systems to reduce the possibility of viruses propagating in the future. HEPA filtration systems are very successful at capturing and removing airborne particles, bacteria, and other contaminants from the indoor air of a facility.
HEPA stands for high-efficiency particulate air. It is crucial that your HVAC system be built with sufficient fan power at the air handling units (AHU) to support their use because installing a HEPA filtration system will have an impact on how the air is distributed.
On AHUs that supply negative pressure zones, think about installing HEPA filter racks. Another alternative is to install HEPA racks in air handlers that you won’t use during regular operations; you’ll only utilize the HEPA filters in a pandemic.
This would allay any worries about the expense of operating and maintaining HEPA filters. Another choice would be to install connections for transportable negative pressure devices with HEPA filters in a dedicated exhaust air duct that leads outside.
2. Air Handling Unit (AHU) Recommendations
Consider designing your AHUs to handle dual conditions for heating and cooling coils: a minimum outside air intake for normal conditions and a 100 percent outside air intake for pandemic and emergency conditions. This is because it is crucial to bring outside air into hospitals in a pandemic situation. For these circumstances, standby heating and cooling capacity can be set to use more outside air.
This would encourage more hospitals to construct their facilities with standby cooling equipment and more facilities to employ chilled water cooling systems. Direct expansion systems that utilize air cooling are frequently used in smaller establishments. However, they frequently lack additional capacity to boost outside air without reducing comfort.
The majority of building codes currently call for backup heating systems. The idea would be to utilize the standby capacity in case of emergencies.
At the cooling oils, take into account the usage of high intensity UV lighting or other comparable air treatment devices . They might be successful in destroying a significant portion of virus particles going through the AHU in addition to aiding in coil maintenance.
3. Negative Pressure Environment Recommendations
Since air naturally moves from areas with higher pressure to areas with lower pressure, negative pressure rooms have mechanical ventilation systems that keep the pressure of the room at a level that is slightly lower than the pressure of the entry area. This prevents contaminated air from the isolation room from escaping outwards.
Negative pressure room construction calls for extra cara to be taken with small details, such as caulking all wall penetrations and using monolithic gypboard ceilings. Also frequently employed are door sweeps and seals. They are consequently far more expensive to build.
Negative pressurization may be hindered when transforming ordinary rooms into negative pressure environments due to fixed design elements. The measured pressure differential could be lower than anticipated even when correct directional airflow can be accomplished.
4. Return Air and Exhaust Air Recommendations
A new hospital’s design should take into account return air and exhaust air best practices in addition to the importance of outside air intake. In certain configurations, mechanical rooms get return or relief air discharges. In order to lower the risk of infection and enable return fans to be used for emergency exhaust, future projects should steer clear of this and have all return air ducted to the outside.
In isolation rooms, return air grills must be placed over the patient’s bed or in the headwall to comply with code. Moving future, perhaps the return grills for med/surg patient rooms could likewise be located on the headwall rather than at the entry. For non-infected people who are prone to infection or immunosuppressed, a doorway placement is more suitable.
The placement of the return grilles in the med/surg patient rooms should be carefully examined with the hospital during design because these are two competing orientations. Consider installing two return air grilles, one by the door and one by the bed, each sized for 100 percent airflow, in the patient room. With it, the facility could isolate one of the grills depending on whether it was operating in regular mode or pandemic mode.
The pressure relationship in a room cannot be switched or changed from positive to negative under the current code. However, if procedures are put in place during switchover, the code might be reevaluated for these circumstances. The primary issue is that the rooms are not actively changed. A coordinated approach that has been approved by the hospital and code authorities is required for switching room pressure relationships.
On the return side of each patient room, air valves or air terminal units can be utilized to automatically change the airflows and room pressures without the need for manual rebalancing. However, the cost of implementations is high. This arrangement is required by some jurisdictions.
Reduce the usage of flexible ducts for return and exhaust air regardless of the design that is used; they are readily blocked by lint and dust, which drastically lowers airflow.
5. Ventilator Support Recommendations
Obtaining the necessary volumes of medical-grade air and oxygen to sustain the ventilators needed to treat the sickest patients was one of the COVID-19 refit projects’ most difficult challenges.
It’s crucial to precisely predict future ventilator loads while creating a new hospital. It is challenging to convert conventional med/surg beds to ICU/CCU beds because ventilators need access to medical grade air in addition to oxygen. Consider building larger pipes when designing future hospitals since they can accept far more medical air or oxygen for a lot less money than it would cost to retrofit a med/surg floor, making it simple to convert med/surg floors to ICU/CCU beds.
The minimum size for medical air and oxygen on patient floors should be 34 inches, and runouts to individual rooms should be 1 inch and a half. In cases when a higher ventilator load is anticipated, larger sizes may be acceptable. Since not every patient will require the same quantity of medical air and oxygen, patient diversity is another aspect to take into account.
With the hospital, you must go over normal or ideal ventilator settings. When only a small number of ventilators need to be accommodated, diversity is frequently overlooked, and conservative values have historically been applied.
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