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Know JackAbout IAQ

IAQ and the

Four Ps

by Jack Springston CIH, CSP, FAIHA

26 September 2015


or this month’s article, I thought it might be a good idea to go back to some basics regarding indoor air quality (IAQ) issues. Before I go any further, however, I need to give a big shout-out to my friend Mike McGuinness. It was during a conversation that he and I had at this year’s Building Sciences Summer Camp that he reminded me about the four Ps in IAQ. This concept has been discussed in depth elsewhere in other publications, but it never hurts to reintroduce it from time to time. Whenever we are dealing with building occupant complaints and adverse health effects, it is important to remember that there are a series of links in the chain of causation. For IAQ problems that are caused by exposure to some sort of airborne contaminant(s), the chain of causation can be boiled down to a fairly simple (at least on paper) equation: Poll + Path + Pres + Peop = Prob Where: Poll = Pollutants Path = Pathways Pres = Pressures Peop = People Prob = Problems That’s it. There’s really not all that much to it, once you understand the principal and the mechanisms behind it. If you can break any one of those links in the chain, then you can usually resolve the problem. So, with that said let us take a closer look at the first four “Ps.” Pollutants Pollutants come in a variety of forms. There can be particulate pollutants, such as diesel fumes, pollen, or smoke; vapor pollutants, such

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as formaldehyde and other volatile organic compounds from laminate flooring, furnishings or paints; or gaseous pollutants, such as carbon monoxide or nitrogen oxides from combustion sources. They can come from manmade sources, such as exhaust from laboratory fume hoods or kitchen exhausts, or from natural processes, such as smoke from wild fires or microbial growth as a result of water intrusion. Sources of pollutants can be from either outside the building, such as soil gas or exhausts from vehicles and nearby buildings, or from within the building, such as emissions from copier machines, use of cleaning products, or from the occupants themselves (e.g., perfume, body odors, cooking, etc.). Often, the pollutant source causing the problem can be determined by identifying the pathway that it is using to reach the affected individuals. Pathways Buildings usually have numerous different

pathways through which pollutants can migrate. Air handling systems can draw in pollutants through the outdoor intakes, or via the return air ducting, and distribute them throughout a building. Stairwells, elevator shafts, utility shafts, conduits and other penetrations, both between floors and in the building envelope, all can act as pathways for pollutants. The movement of people through a building, and their actions, can have a large impact on the movement of pollutants as pathways can be created and changed as doors and windows are opened or closed. Even small holes or cracks in walls and foundations can allow significant amounts of air through them if there is a big enough pressure differential from one side to the other. I one time had a situation where the occupants on one floor of an office building in midtown Manhattan were complaining about intermittent cigarette and marijuana smoke odors. The building shared a common masonry “exterior�

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wall with an adjacent Broadway theater. When we investigated further, it turned out that there was a breakroom for the ushers on the other side of that common wall, and that the ushers liked to relax with a smoke or two during their downtime. Although there were no obvious penetrations in the common wall, it was clear that smoke and odors from the usher’s breakroom were being drawn from that space and into the adjacent office building due to pressure differentials. Pressures

the most obvious of which is a building’s ventilation system. Exhaust fans, not surprisingly, create negative pressure and cause a building to suck (as in, air gets sucked into the building because the building is at a lower pressure than outside). If you do not control where the makeup air is being pulled into the building then it can, and will, be pulled in through any and every opening in the building envelope. Generally speaking, when it comes to IAQ, buildings that suck are not a good thing and really should be avoided.

Supply air ventilation systems, on the other Pressure differentials are the primary forces that hand, tend to make buildings blow (as in – yep, you guessed it - air gets blown out of the builddrive pollutants from point A to point B. Sure, ing because it is at a higher pressure than you can get some movement through passive outside). Now, while this scenario is somewhat diffusion, where contaminants move from an better than if your building sucks, it can still area of high concentration to an area of low potentially lead to problems. Pollutants that are concentration in an effort to reach equilibrium. generated in one area of a building, say from However, diffusion tends to be a rather slow a copier machine or from a kitchenette, can be process. Pressure differentials, on the other pushed to other areas of the building unless hand, can rapidly move and distribute contamisome sort of local exhaust ventilation is providnants throughout a building. ed. While that type of problem is pretty simple Pressure differentials can be created by a num- to fix, you need to make sure you make provisions for controlling where the make-up air is ber of different mechanical and natural means,


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coming from. However, what if you have occupants in one area who wear perfumes and colognes, while occupants in an adjacent area are sensitive to such products? That can be quite a bit more difficult to address. Indeed, I was involved in one case where occupants on an entire floor actually evacuated the building due to an unfamiliar and unidentified odor. It turned out that an employee went to apply perfume on herself and somehow spilled the contents of the bottle. Natural forces can also cause pressure differentials within a building, resulting in air movement between different zones within the building and between the interior and exterior of the building. Wind blowing against the side of a building can create local areas of high pressure on the windward side, forcing air into the building, and areas of low pressure on the opposite, leeward side, where air is being pushed out of the building. It can also cause pressure differentials within and between rooms inside the building. Stack effect (a.k.a. chimney effect) is another natural force that can cause pressure differentials within a building. The driving force for stack effect is pressure differentials created by the tendency of warm air to rise. As the warm air rises and escapes out of the upper levels of the building, outdoor air is pulled into the building on the lower levels through any openings that it can find. This air movement can pull pollutants into the building and transport contaminants between floors of buildings. This effect occurs when there is a difference in the air temperature inside the building versus the air temperature outside of the building, and becomes more and


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more pronounced the greater the difference in temperatures. Stack effect can be particularly strong in skyscrapers and high-rise buildings in temperate zones during the winter months. People This is one link of the chain that really cannot be controlled to any great degree, or reasonably be broken short of vacating the building. For the most part, buildings tend to be occupied by people. Sure, we have some buildings that are rarely occupied (think self-storage units), but how often do you ever hear of people complaining about the air quality in one of those types of buildings? Generally, when we talk about building occupants we are referring to those people who actually work within the building and spend large amounts of time there. However, most buildings have clients and other visitors who occasionally visit and who are likely to have very different tolerances and expectations regarding the air quality. Such individuals are also likely to be more sensitive to certain odors within the building than are the regular occupants. I one time did an IAQ investigation at a facility that manufactured fragrances. While I perceived the odors within the building as being overpowering, to all of the employees who worked there day in and day out, it was completely normal. Another thing that needs to be kept in mind with regard to building occupants is whether or not any of them have underlying health conditions that would make them susceptible to certain pollutants. Is the building that you are

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investigating full of relatively healthy workers, or is it occupied by predominantly sick and immunocompromised patients? That can make a huge difference when trying to determine if the concentration of pollutants within a space are of any significance or not. It is important to remember that in your typical office building you will usually encounter a wide variety of occupants with varying sensitivities. It is not all that uncommon to have one or two individuals who react to a particular pollutant or condition, while the surrounding occupants are fine and show no ill effects. Share YOUR comments on our LinkedIn discussion by clicking the button below!

Jack Springston, CIH, CSP, FAIHA, is a Senior Project Manager at TRC Companies and PastChair of AIHA’s IEQ Committee. Jack is an industrial hygiene consulting professional with over 27 years of experience in recognizing, evaluating, measuring and controlling employees’ exposures to health hazards in their workplace. He has been a Certified Industrial Hygienist since 1993, and is one of only approximately 60 CIH’s who also currently have a sub-specialty certificate in Indoor Environmental Quality, and a Certified Safety Professional since 1996. Jack has participated in and overseen hundreds of indoor environmental quality studies, both investigative and proactive, in over 50,000,000 square feet of building space.

Fragrance-Free Workplaces? In the 1960s few would have believed that smoke-free workplaces would before long become the norm. Could fragrance-free workplaces be the wave of the future? A CDC policy bans the use of air fresheners and scented candles in every CDC facility in the country. This policy states: “The use of some products with fragrance may be detrimental to the health of workers with chemical sensitivities, allergies, asthma, and chronic headaches/migraines.” The full CDC policy can be viewed on the website of the Chemical Sensitivity Foundation, which contains information about multiple chemical sensitivity (MCS), including a research bibliography. Individuals with MCS react not only to fragrances but also to substances such as cleaning products, pesticides, diesel exhaust, air fresheners, fabric softeners, and new carpet. Symptoms can include asthma attacks, sinusitis, headaches, skin rashes, irritable bowel symptoms, fatigue, and difficulty with concentration, memory, and cognition.

To learn more, play on YouTube the video “Multiple Chemical Sensitivity: A Life-Altering Condition,” which contains footage of interviews with four leading members of Congress and a former Commander of Walter Reed Army Medical Center.

Healthy Indoors - Sept 2015