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Pressure Critical Rooms Tech Talk

Stacy Carey and Steve Jerge, Midwest Associates President and General Manager respectively, presented at the Building Commissioning Association June 2020 Tech Talk.

Along with representatives from Grumman/Butkus Associates, Stacy and Steve discussed commissioning and balancing Pressure Critical Rooms (PCRs), such as operating rooms, ICU rooms, cleanrooms and laboratories.  PCRs have very specific design, construction, and performance requirements that must be adhered to, tested, and documented. This year we’ve seen a sharp increase in the need for commissioning PCRs and creating new, makeshift PCRs for treating and testing COVID-related patients.

Our Midwest Associates team shared their years of experience commissioning and balancing PCRs and the lessons they have learned along the way to help avoid common errors.

Here are a few highlights from their presentation.

A TAB technician’s process for balancing a PCR involves the following key steps:

  • Review the drawings and specifications to understand the room requirements – for example, does the room need to have positive pressure, negative pressure, or a pressure cascade (ensuring the flow of contamination is from clean to less clean); what is the required ACH (air changes per hour)​.
  • Visually inspect the room envelope integrity.
  • Pressure test the room if required by the owner.​
  • Balance the room to design​: test and adjust all supply valves, boxes, diffusers and all exhaust valves, boxes, grilles.
  • Measure the pressure differentials using a multimeter and compare this data to the room sensor or monitor readings​.
  • If balancing multiple rooms with a cascade, start with the innermost room and “work your way out.”​
  • After the pressure differential is correct, measure the room and calculate the ACH​. The ACH is a measure of the air volume added to or removed from a defined space divided by the volume of that space. In other words, this is the number of times per hour the total volume of air in a room is changed over.

 Commissioning and TAB lessons learned:

  • Before they can complete their functional testing, commissioning providers need to review the TAB report. If a commissioning provider has any questions regarding the report, don’t hesitate to call the TAB firm and ask. Commissioning providers and TAB contractors can and should work together to achieve the best results.
  • In most cases, the initial balance to the design airflows doesn’t achieve the required pressures. TAB technicians should discuss adjustments with the design engineer.
  • Keep in mind that most balancers will measure room dimensions without taking cabinetry, bulkheads, etc. out of the room.
  • Verify the TAB instruments are within calibration​.
  • Low level return grilles can get loaded with lint from bed linens. It’s a good practice to clean them before starting balance​.
  • Best practice is to inspect the AHU and exhaust equipment, including the pressure differentials, before starting balance​.

An Overview of ASHRAE’s Updated Guidelines for Academic Buildings

The reopening of schools and universities has been a prevalent topic these past few months as institutions strive to ensure they’re providing the safest possible environment for their students and staff to learn and teach in.

It is important academic leaders continue to review and verify their plans for reducing the spread of viruses like COVID-19 are up-to-date and being followed.

At a conference this summer, the ASHRAE Epidemic Task Force presented an updated guide to reopening schools and universities, reaffirming their position that “Transmission of SARS-CoV-2 through the air is sufficiently likely that airborne exposure to the virus should be controlled. Changes to building operations, including the operation of heating, ventilating, and air-conditioning [HVAC] systems, can reduce airborne exposures.”

The collection of 41 slides includes a series of checklists to be completed for specific equipment and systems throughout the academic year. Some checklists are to be done daily such as general cleaning and flushing the air by operating the mechanical systems in occupied mode for at least 2 hours before occupancy.

Most equipment and system checks should be done on a monthly basis. Some of the monthly checklists are for major pieces of equipment like air handler units, boilers, cooling towers, and chillers. There are also checklists for single zone equipment like fan coil units and mini-splits, as well as water and steam distribution systems.

The Task Force outlines a set of “Designer Guidelines” with the goal of helping “designers retrofit and plan for the improvement of indoor air quality and to slow the transmission of viruses via the HVAC systems. The underlying effort of the designer should be to increase outside air to the spaces, treat return air and or supply air to spaces via mechanical filtration and maintain indoor comfort as defined by the design temperature and relative humidity.”

The guide also provides instructional and procedural recommendations for how facility managers can increase their existing air system’s filtration efficiency during the pandemic. The target filtration level for schools is currently MERV 13 or higher. The slides walk you through how to gather the necessary data to determine whether MERV 13 filters are compatible with your system. If MERV 13 cannot be installed, they offer alternative options for increasing filtration.

Finally, the updated guide includes a list of protocols for higher education facilities to implement, including recommendations for unique spaces like student health facilities, laboratories, athletic facilities, and residence halls.

Midwest Associates is here to help you evaluate and test how your academic buildings are performing this school year. Visit our contact page above to learn more about how our services can benefit you. To learn more about ASHRAE’s reopening recommendations, visit the link here: https://www.ashrae.org/technical-resources/reopening-of-schools-and-universities