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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​.