By Gary Wilkins
At some point in your life, you probably owed one of your teachers an apology for muttering, “I’ll never use that in the real world,” only to later discover your teacher was right. Many learnings have real-world applications — only sometimes do they come later in life. When I think back to my own-owed apologies, I recall another statement — “junk in is junk out” — as it relates to the use of calculators.
That “junk” is exactly what this article is about.
As a firefighter in today’s world, you’re conducting more math and science than you ever thought possible. When speaking with firefighters, the most hot-button calculation across the country is friction loss and gallons per minute (GPM). Manufacturers publish data knowing that fire departments can easily confirm those figures. In fact, most firefighters have probably spent money on fancy water flow meters that send real-time data to their mobile phones, and if not, many can recall using the ever-reliable pitot gauge to catch manufacturers in the occasional lie.
Unfortunately, data from other parts of the fire industry remains unchecked. Take for instance ventilation. There are no real measures to properly (and fairly) evaluate fans while in the field. Flashing back to our “junk in … junk out” statement, if you’re basing your training on uncertified data, then the result is junk out.
Looking at ventilation at its most basic level, the measurement of CFM (cubic feet per minute) can be used to approximate the amount of time it takes to effectively ventilate a structure.
But how can you trust the manufacturers’ published CFM? There are no readily available gauges that firefighters can carry in their pockets to confirm this reported data.
So that’s where third-party airflow certification comes into play.
The Air Movement Control Association (AMCA) has become recognized as the authority for the development and measurement of airflow. Specifically, the ANSI/AMCA 240-14 was developed to measure and compare effective airflow of positive pressure ventilation (PPV) equipment. This test was developed in 1996 to provide end-users with trusted and repeatable airflow measurements that include the effects of entrained air. And recently, the AMCA 240 Committee developed the first method of testing the performance of a battery-operated PPV. This new standard is scheduled to be released in 2022.
But standards and data are only good if departments look for this information (and demand that all manufacturers provide these important numbers). The manufacturer must label their numbers as “AMCA Certified.” If they fraudulently make this claim, AMCA can take action against the manufacturer. And if the manufacturer uses AMCA Setup,” “AMCA Accredited” or any other phrase, their numbers are not verified and a field test should be executed. Again, the numbers shouldn’t be junk.
AMCA’s reputation extends to the NFPA, where this organization has leaned on the association when creating NFPA building codes pertaining to ventilation, like the following codes:
• NFPA 80
• NFPA 90A
• NFPA 90B
• NFPA 92
• NFPA 101
• NFPA 105
• NFPA 204
• NFPA 5000
And while this article could dive deep into the depths of AMCA, we’ll simply reference one of AMCA’s most recent webinars, bit.ly/amca-240-webinar, and instead, focus on what you can do in the field to evenly compare airflow when this data isn’t readily available. Most major (and reputable) brands of positive pressure ventilators have taken the extra steps to provide the fire industry with certified equipment, but in the instances where you’re evaluating uncertified equipment, you can take measures to standardize your department’s own evaluation process.
You’ll notice we said, “compare airflow” — not “certify airflow.” Without the proper setup, equipment, and knowledge, it’s impossible to fully certify positive pressure airflow in the field, but a simple wind meter (commonly used for landing a helicopter or to get a weather update on wildfire incidents) can be used to provide a few decent, comparable measurements. Again, though, these readings are not the “most accurate.” They’re simply a means of providing “comparable results.”
The importance of the evaluation cannot be understated, and for ventilation evaluation, the following recommendations allow you to evenly compare ventilation equipment across every manufacturer. Here are some step-by-step guidelines:
1. Set up equipment according to manufacturer recommendations, as is recommended in the 7th Edition IFSTA Manual.
a. For instance, manufacturers offer various guards, which allows the fan’s setback to vary based on the department’s needs. As such, the fan’s position (based on manufacturer guidelines) becomes extremely essential. Moreover, AMCA scientific results show that proper setup can increase entrained airflow, which in turn can double the effective airflow when the equipment is used properly.
2. Evaluate all fan manufacturers during the same day, within the same environment, roughly the same time.
a. Humid air is less dense than dry air. Crazy as it may seem, it’s true. As the time-of-day changes, the humidity in the air also actively changes. In most cases, slight variables will only affect the results by a few percentage points, but major changes can impact your evaluation. For instance, if you were to evaluate Fan A at 800 with 20% relative humidity and then evaluate Fan B at 1600 with 80% relative humidity with an impending rainstorm, the results will be drastically different.
b. The same can be said for wind speed and direction.
3. Use the same test structure with the same entry point and exit point per your department’s operating guidelines for proper ventilation.
a. If possible, when using a portable wind meter, try and secure it to a stationary point in the center of the exit point, allowing you to receive consistent measurements and remove the human variable from the results.
To that end, it’s important to try to eliminate as many variables as possible during the evaluation, focusing on maintaining the same setup — or a near-identical setup as possible — and removing as many external factors as possible, like wind speed and fan direction. Also, be sure to measure the exit speed winds at the same exit point between the different brands. Performing this kind of evaluation can provide you with some knowledge of how much wind is moving through the structure. However, please note this wind meter measurement is only MPH and does not account for the amount of air moving throughout the structure, so the ventilation calculation mentioned earlier does not apply to this result.
In the end, a detailed equipment evaluation of features and benefits along with verified data is critical in the selection process, ensuring that some fast-talking salesperson doesn’t persuade your department with too-good-to-be-true numbers. Take a moment to confirm reported airflow numbers at amca.org/certify/#certified-product-search, and when all else fails, break out your own meter.
Gary Wilkins has spent the last three years focusing on all-things ventilation, working for Super Vac, one of the world’s most experienced ventilation companies. Prior to that, he worked in North Carolina as a distributor sales representative in the piedmont. Additionally, he notched 14 years with the Northeast Stokes Volunteer Fire Department and currently serves as a resource and advisor to the department and community in equipment evaluation and purchasing.