Addendum to “Indoor Air Quality vs. Water Quality”

Addendum Blog by: Eric Knight of Orenda Technologies

Air Quality Guest BlogThe previous post Indoor Air Quality vs. Water Quality: Indoor moisture and how to combat it did a good job covering the basics of indoor air quality in pools. This addendum in blog format is to expand upon that article and introduce more facts about the problem.

While water and air quality are closely related, perfect water quality cannot ensure good air quality

For some reason, there is a myth being pushed in the pool industry; a myth that suggests all air quality problems can be stopped by addressing water quality. This idea is widely believed and is even promoted by influential organizations such as USA Swimming

“Water Quality has to be correct. 99% of the problems that are tagged as air quality are caused by chloramines or other contaminants in the water. Until this problem is solved, the problem will remain. Treating the air first is like trying to treat the smoke before putting out the fire.”

Their statement blames air quality problems on water quality, when there is far more to the equation beyond water chemistry. Air physics are involved too. To adequately solve the problem, a broader understanding of indoor pools is needed, as well as a willingness to think differently. Clearly, indoor pool designs for the past several decades have not worked well enough.

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Fact: Even with excellent water quality, air quality can still be a problem. There are plenty of bad indoor air quality cases where pools have state-of-the-art filtration, UV, and are under excellent management. It is not always a reflection on the operator and equipment; air is far more difficult to control (and test) than water.

Why do so many experts focus their minds on water chemistry at the expense of all other factors? To refer back to USA Swimming’s statement, it’s like putting out the fire and believing there will be no smoke in the process. 

Anyone who has blown out a candle knows that doesn’t make sense. The smoke is inevitable, and therefore must be addressed. Bad air quality is not water chemistry’s burden to solve on its own.

Air quality problems can be solved, but only when addressed from both sides of the issue

The moment disinfectant byproducts (DBPs) off-gas into the air is the separation between water and air quality. After the moment of off-gassing, water chemistry is irrelevant to the airborne contaminants; all that matters now is the air system and the airflow it provides.

Fact: Most indoor pool air systems are inadequately designed. That’s not to say they are “wrong”, because the air systems and designs [should] meet ASHRAE 62.1 standards. Issues arise because there are many ways to interpret the ASHRAE code, and while 62.1 makes firm recommendations for indoor pools, the section is only a couple pages long in the handbook. Compare that to multiple chapters for other applications, and you will realize that engineers designing pools have very little framework to follow.

In reality, many of these mechanical engineers wisely seek help from pool experts and consultants. And yet, until some recent breakthrough technology changed what pool air systems are capable of, problems would still often arise.

Fact: There is a difference between “return” and “exhaust”. Returns draw air into the pool dehumidification unit (PDU), which exhausts a portion (usually 10-20%) and conditions the rest to be resupplied into the natatorium. Low returns in pools have been prevalent, but they actually do more harm than good. By placing air intakes low to the ground, airborne DBPs like chloramines get recirculated throughout the entire natatorium…corroding everything along the way. This is why pool dehumidification systems lose coils, compressors, fans (among other components) to rust and corrosion. Ask any pool owner who has had to replace these parts…they are not cheap.

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Exhausts are not returns. This can get confusing—mostly because of semantics—but it is an important distinction to make. In most applications, returns are synonymous because the exhaust fan is within the return path. This should not be the case in a pool system. It is essential to keep the exhaust separate from the PDU. Recirculation of chloramines is a sure-fire way to exacerbate an air quality problem, and damage the equipment in your facility—and indeed, your facility itself.

Fact: Opening outside doors during the winter can make air quality worse. Since the natatorium should be negatively pressured, the cold air is sucked into the room, but allows for the vapor pressure to escape. A sudden reduction in vapor pressure means easier and faster evaporation, which can mean more airborne chloramines. Not to mention the tremendous stress on the PDU, which was designed for a certain amount of moisture removal. When cold outside air is introduced, it can overwhelm a dehumidifier, with costly consequences.

Fact: Exhausts within PDU systems cannot distinguish between good air and polluted air; source-capture exhausts, however, make it possible. We hear so much about the amount of outside air introduced, or the turnover rate, or the [insert confusing industry buzzword here]. If you really want to good indoor air quality, a traditionally designed air system will not do it. The duct, PDU, return location, air volumes and style and location of exhausts all matter. A lot. Beware of any expert who thinks otherwise.

Fact: Exhausts and returns are only as effective as the design of the supply duct allows them to be. Air flow in a natatorium is almost completely driven by the supply side of the air system, so it is very important to have it designed right. Getting air to the breathing zone (but not directly aimed at the water) is critical. Once it’s there…make sure it moves somewhere you want it to go—ideally an Evacuator system.

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How water quality can improve—but not prevent—air quality problems

On the other side of the equation is water quality…but as stated before, great water alone will not prevent bad air quality. You can clean your shower every day, but that won’t stop DBP’s from off-gassing every time you spray it with household cleaner. The key is consistency; consistent management of chemistry, high ORP, balanced LSI and pool cleaning practices. With heavily loaded pools, the introduction of organic waste is a given.

Fact: Chlorine does not distinguish between non-living organic waste and living bacteria/diseases; it just oxidizes and sanitizes whatever it can. When chlorine gets used up, however, partially oxidized organics often become DBPs. This is why it is important to help chorine by breaking down organic waste beforehand. That way, chlorine doesn’t get burned up as fast, ORP stays high, and it’s able to disinfect living organisms faster. Some proven ways to help chlorine address organics are enzymes, ozone and UV. Enzymes can be combined with either ozone or UV as well.

Circulation, filtration and sanitation. They are the three pivotal aspects of water quality, and each of them need to be on point. Breaking down organics, for example, can reduce chloramine byproducts in the water and air, but without good circulation, only part of the pool will benefit. Without adequate free chlorine levels, sanitation will fall behind. If the water chemistry is consistently balanced properly and organics are addressed, less DBPs should off-gas, which means an improvement to air quality.

Let the air system with source-capture exhaust handle it from there.

Air Quality Guest Blog NSPF

Guest Blog Eric KnightWhen Eric Knight was a swimmer, he developed asthma and needed an inhaler during workouts and swim meets…which is not uncommon in the sport. Knowing how harmful this air actually is, adequately ventilating it and managing water chemistry is personal to Eric. With Paddock, he spent years visiting hundreds of pools with bad air quality, working directly with engineers and other HVAC experts, and learning countless examples of “what not to do” with pool ventilation.  Now, Eric has shifted to the water side of the problem to help address the production of chloramines and overall water quality. After experiencing what Orenda products do (by swimming in Orenda-treated pools), the difference is clear. Learn more about Paddock Evacuator and Orenda. Contact:



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1 comment on "Addendum to “Indoor Air Quality vs. Water Quality”"

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    After reading this "Adendum", it's surprising to me that the chemists aren't here defending the "water quality" assertion to this Industry problem. In my HCF interpretation last year, I explained how water treatment systems got "dummied down" so that manufacturers can be competitive in the market. The re-introduction of properly configured water quality control systems, which conform to the HCF specification that I introduced, has been proving my claims of an odor free pool consistently. If you don't ensure that the fundamental chemical reactions are occurring in a manner proportional to the demands the pool is presenting, your pool will only exacerbate the issue, and it will get worse as you progress. Here's what we know TODAY, about HCF: Hyper dosing chlorine into a pool using aggressive controller programming reduces the creation of di and Tri Chloramines, the two versions of DPB's that create the issues that we have been trying to mitigate. Monochloramine is kept no higher than 0.5 ppm, yet the pool space is odor free (Monochloramines do not give off an odor) Maintaining chlorine residuals below 2 ppm is achievable with HCF use, and HCF pools are relatively odor free. When pools are busier or are over utilized, while odor is minimized, there have been reports of eye burn in some HCF pools; upon evaluation of the HVAC systems in these pools, we found that they are not performing as intended, and, when these performance flaws are corrected, these issues go away. Simple changes, like replacing air filters with ones that have an activated charcoal layer, help reduce DPB's in the air, improving air quality further. As for the idea of adding exhaust ducts to blow the problem air out of the pool space... why do what a properly working HVAC system is already doing? Companies like Dectron and PoolPak complain that adding these systems only overwhelm their equipment, and only results in poor environments for swimmers, as the air is uncomfortable, as it is not humidified or heated properly. An HVAC System has to 1) allow the MINIMUM 9 air exchanges per hour as per Industry guidelines, 2) adjust that air exchange when pool conditions require it... the agitation of water by swimmers increases humidity and DPB gas off, so a surge of humidity should signal the system to open the dampers more and increase the air exchange. This would allow for a reduction of any DPBS in the pool to be kept at bay. As far as I'm concerned, these options are already provided by the leading companies.Adding exhaust fans to a controlled space only increases the entropy of the space, and creates issues that affect the end user's pocket in the end. Adding HCF to your program, and ensuring that your HVAC system is operating as intended, will ensure a safer environment, with less hassle, and reduced costs.