ASHRAE 170 Compliance: Ventilation of Health Care Facilities

Space pressure relationships, air exchanges, relative humidity, and temperatures all play a vital role in healthcare facilities’ daily operations. Considering healthcare-associated infection rates and the global pandemic (COVID-19), healthcare facilities’ environmental conditions are more relevant today than ever.

ANSI/ASHRAE/ASHE Standard 170, Ventilation of Healthcare Facilities, defines design requirements for environmental control, but who is responsible for verifying the systems are compliant prior to construction, before occupancy, and throughout the life of the systems? This paper will tackle real-world challenges facing ASHRAE 170 compliance from a commissioning provider’s perspective.

Design Challenges

During the design phase, the number one challenge, which almost always leads to compliance issues down the road, is the lack of specifying testing requirements. Unless the contract documents specifically require verification of ASHRAE 170 compliance, it becomes a toss-up whether the actual performance is adequate for the spaces’ function.

But what about the Testing, Adjusting, and Balancing (TAB) firm? Aren’t they contracted to balance the systems to the design? Balancing the mechanical systems within the allowable tolerances and ASHRAE 170 compliance verification are entirely separate tasks. Most reputable TAB firms are undoubtedly capable of both tasks, but the latter will not occur unless specifically required in the contract documents. Simply put, no services are free, and in a competitive market, competitive pricing is invaluable.

To receive a quote, the quote must first be requested. Furthermore, systems being in tolerance with the design does not mean the spaces are compliant with ASHRAE 170 requirements. What if that -10% tolerance puts the system below the required air exchanges per hour (ACH), or the designed 100 CFM supply/exhaust air offset is not enough to maintain the necessary pressure relationship?

So, who is responsible for compliance verification? Per many contract documents, no one is required to verify compliance, and the hospital inherits latent design or construction issues. To make matters worse, the patients also inherit these issues. Ventilation issues are often identified as the hospital preps for accreditation or during the accreditation process itself, which is sometimes close to the end or after the project’s warranty period – leaving the owner little recourse. Also, no inspection process is perfect, and it is not uncommon for ventilation issues to go unresolved for years.

When spaces have pressure relationship requirements, a whole new set of challenges apply. Not only does the mechanical design need to account for pressure relationships, but the architectural design must be factored in, too. Commonly, the designed airflow pressurization offset cannot overcome leakage through the space’s envelope, leading to insufficient pressurization at the main entryways.

Addressing pressurization issues during construction (usually a few weeks before turnover) can be tricky. Replacing or modifying mechanical equipment is challenging at best or practically impossible at worst, but sealing wall penetrations and installing door gaskets is comparatively easy. However, if not already designed, costly change orders and project delays ensue.

Another challenge facing ASHRAE 170 compliance is room naming conventions. It is quite common for room names to be different from the “Function of Space” listed in the ASHRAE standard. For example, suppose a gastrointestinal endoscopy procedure room is named “procedure room.” In that case, it will not be clear what the function of the space is, as there are different requirements for endoscopy procedure rooms and rooms intended for other surgical procedures. Furthermore, if the endoscopy procedure room is additionally used for bronchoscopy procedures, then additional requirements are applicable in that case too. Though simple, naming conventions matter.

Just because an operating room requires a minimum of 20 ACH does not mean the room should be designed for precisely 20 ACH. Similar to heating load calculations, a buffer is needed to compensate for different variables and unknowns. Likewise, this buffer needs to leave room for field adjustments and system tuning. In more cases than not, field tuning is required to bring spaces in tolerance with ASHRAE 170 standards, especially when it comes to pressure relationships.

Construction Challenges

During construction, the question is not, “Will issues be encountered?” but rather, “When will the issues be encountered?”. Deficiencies during compliance verification are inevitable. Success depends on upfront planning, quality control, and the allotted timeframe to address problems. If the project’s schedule is compressed, the quality control suffers. Likewise, compliance verification suffers due to a lack of quality control. Furthermore, if compliance verification is occurring the day before occupancy, resolving problems encountered is unlikely.

Testing Challenges

In the event the contract documents require ASHRAE 170 compliance verification or the hospital contracts a testing agency, numerous challenges can be encountered. While not an exhaustive list, the following are examples of real-world observations.

As a commissioning provider, we have observed spaces compliant after construction but fail a few short months later. Compliance longevity of critical hospital spaces is dependent on many factors. A common source of failure is seasonally based. If testing occurred during mild ambient conditions during the spring or fall seasons, temperature and humidity ranges might not be adequate during peak winter or summer loads.

If an operating room were tested during the humid summer months, humidification control likely could not be fully proven before turnover. During dry transitional periods, especially during full economizer (100% OA), often humidity control issues are quickly identified by surgical staff. For spaces that require positive pressurization, minimum airflow scenarios are favorable, as the air handling unit’s total return airflow is lower across the system.

Suppose a clean holding room with a constant volume supply airflow setpoint was compliant during the winter season’s peak. During the summer season, pressurization may become problematic as the total return airflow has increased, decreasing the supply/return airflow offset within the clean holding room.

It is essential to understand the worst-case scenario and what state the adjacent spaces are in after occupancy. Pressure relationships can be tricky. If testing focuses solely on the room tested, unforeseen compliance issues may arise down the road. For example, does the adjacent corridor door affect the pressurization of the tested space? During occupancy, is said door ordinarily open or normally closed?

Furthermore, what state is the VAV system in – maximum airflow, minimum airflow, or somewhere in between? Or how about that extensive exhaust air system that is off due to a VFD fault? Even if the space itself is constant volume, the surrounding systems make an enormous difference.

Another challenge we all face is human error. Often due to a lack of attention to detail. Mistakes made while measuring room volume, forgetting to check both the total and outdoor ACH, taking pressure measurements at the corridor but not the adjacent spaces, and not verifying the filtration type are all real examples of compliance issues. On the surface, it may seem like the room “passed,” but if adequate time is not allocated to review all aspects of compliance, you are setting yourself and the customer up for failure. Taking the time to understand ASHRAE 170 standards and reading all the notes and the addendums is crucial.

Many hospital rooms merely require negative or positive pressurization, with no numerical pass/fail criteria provided. It is far too common to see tested rooms “pass” when the measured pressure is 0.0001 In. w.g. (essentially neutral), or when the measured ACH is precisely the minimum required amount. As aforementioned, a buffer is needed to account for instrumentation accuracy, as well as fluctuations inherent to mechanical systems. In addition to bringing spaces in compliance with the standards, system longevity should be a goal, too.

Hospitals often consist of many renovations and additions, and the time between these renovations and additions can be decades. ASHRAE-170 is incorporated into the FGI guidelines (the basis of hospital design and construction). It is essential to know which version of the FGI guidelines and subsequent ASHRAE 170 standards are applicable when testing existing hospital spaces. If ASHRAE 170-2017 applies to a renovation project, but ASHRAE 170-2008 is being used to determine pass/fail criteria, inherently, compliance issues will arise, and the same is true vice versa.

Solutions?

Compliance Verification

Traditional TAB services are not enough. Verification of ASHRAE 170 compliance should always be performed regardless of the contract documents. Much like Building Systems Commissioning, it is invaluable to both the owner and the construction team – at the end of the day, all parties know the job was done right.

There are two common approaches to fill the void between TAB and ASHRAE 170 compliance verification. First, the owner can contract a third-party firm directly. As a technical commissioning provider, we identified a gap leading to deficiencies post-warranty phase and began providing compliance verification as a commissioning service. If process-based commissioning is provided, identify the void during the design phase. Even better, help the owner develop Owner Project Requirements (OPR), so testing obligations are integrated into the contract documents.

Identify & Address Pressurization Issues

Designing pressure relationships of spaces is not an exact science. Nine times out of ten, field tuning will be required and is often outside of the +/-10% design tolerances. A step in the right direction would be first to identify the pressure-critical spaces and then collaborate with the architect to ensure the room envelope is also designed to accommodate the needed differential pressure.

Similarly, the commissioning firm or testing agency should review the architectural and mechanical design to gauge the likelihood of maintaining the pressure requirements. If a space is designed for a 30 CFM pressurization offset, has a suspended ceiling, no requirements for sealing wall penetrations, and no door gaskets or sweeps, it is a safe bet the pressurization will not be adequate. The goal here is to collaborate to identify and correct issues as early as possible before becoming time-consuming and costly.

Deleting the Guesswork

When developing our testing plans, every project has at least one vaguely named room, such as “storage 1-101.” The subsequent RFI goes something like this: “What is the function of the room… clean linen storage, janitor’s closet, soiled storage, hazardous material storage?”

Using descriptive room naming conventions is a positive step forward. The room name should incorporate language like ASHRAE 170’s “Function of Space.” The most successful idea implemented to date has been requiring design schedules structured like the tables included in ASHRAE 170, listing all the critical spaces’ ventilation and pressure requirements.

The testing agency must know which version of the FGI guidelines and subsequent ASHRAE 170 standards are applicable for existing hospital spaces. As-built drawings need to reference the date of the FGI guidelines. Likewise, testing forms should also reference where the pass/fail criterion is coming from. In addition to dozens of decade-old design drawings, having a consolidated list of all the critical spaces that require compliance verification goes a long way. The comprehensive list should include the function of the space, room name, FGI/ASHRAE version, the renovation date along with the project name. Bonus points if the pass/fail criterion is also listed.

Technically Passes But Not Really

From PID control loops to filter loading, mechanical systems are dynamic. If a protective environment (PE) room is designed at precisely the minimum 12 ACH required and is balanced to exactly the minimum +0.01 In. w.g. required differential pressure; then the space is sure to fail as soon as the keys are turned over to the owner. Buffers need to be both designed and field-tuned for system longevity.

We’re Out of Time!

A great QA/QC program begins with a realistic project schedule. Developing a schedule that accounts for the time needed to perform testing, identify issues, and address problems is imperative. Furthermore, allocating time to achieve QC measures to ensure testing is successful is equally critical. Since this paper is about real-world challenges, let’s be real – there is never enough time.

Innovative solutions must be implemented to meet the demands of fast-paced projects. As aforementioned numerous times, pressure relationships are always unpredictable and time-consuming to correct, especially when the root of the issue is architectural, not mechanical.

Many solutions can be implemented to enhance quality while staying on schedule. One innovative solution we offer is pressure testing the room’s envelope while still in the rough-in phase. Using a blower door and building envelope testing methodology, the room’s airtightness can be assessed for leaks. While still feasible both from a time and financial standpoint, identifying and correcting deficiencies early is invaluable for the finished product’s quality. Not to mention, no one likes to tear down a finished hard ceiling to access and repair air leaks.

Worst-Case Scenarios

As the testing agency, it is vital to identify the worst-case scenarios and how the rooms and adjacent spaces will be used after occupancy. Seasonal changes will affect pressures, air exchange rates, temperatures, and relative humidity levels, all of which have required design parameters for compliance. During testing, various scenarios should be simulated to identify potential problems before they become actual problems. Do the reheat and cooling coils have adequate capacity? Does the humidifier work? How do economizer, minimum airflow, and maximum airflow affect pressurization?

Seasonal testing is necessary, too. While you can simulate many conditions, some issues cannot be identified without the appropriate outdoor ambient conditions. One specific illustration of these issues would be when tuning PID control loops. Additionally, performing traditional seasonal testing at the peak of summer and winter may not be adequate. Unforeseen issues can also arise during heating/cooling transitional periods in the fall and spring seasons, especially relative humidity control.

Attention to Detail (or the Lack Thereof)

At some point or another, everyone has made a mistake. The same is true with ASHRAE 170 compliance testing. We have reviewed hospital spaces that have “passed” but are not compliant in reality. The key to reducing human error is to establish a systematic procedure to alleviate the likelihood of mistakes. This begins with developing a standardized plan and test forms to ensure the accuracy of each test. Often, healthcare systems have multiple testing agencies to test their hospitals for compliance, all of whom have different methodologies, test forms, and procedures. In this case, there is value in standardization at the healthcare system level.

Conclusion

From hospital accreditation to infection control, ASHRAE 170 compliance is vital to healthcare systems and the patients they serve. Compliance presents many challenges during the design, construction, and life cycle of the systems. Whether adjusting contract documents, implementing innovative solutions to improve QA/QC efforts, or improving testing procedures – identifying common issues and implementing strategic mitigation measures is the key to success. While challenging, if it were easy, everyone would be in the market.

Dr. Dale E. Turner put it best when he said, “Some of the best lessons we ever learn are learned from past mistakes. The error of the past is the wisdom and success of the future.” Keep track of the issues encountered during testing. Host lessons learned collaborative meetings with team members and clients. Challenges exist to be overcome.