Have you ever calculated how much urine and sweat are in the average pool? The number might surprise you. All this urine and
sweat (amongst other things) form that nasty, elusive thing we know
as chloramines, which show up as the combined chlorine we see in
our daily tests.
This tells us what’s in the water, but not always
what’s in the air. Nitrogen trichloride, aka trichloramine
(TCA), literally jumps out of the water and into the air. But what
is it made of? Three chlorine atoms attached to the ammonia ion,
which comes from urea, the main component of urine and sweat. So if
you have a lot of chlorine in the water as well as a lot of urine
and sweat, then you’re going to have combined chlorine, the
precursor to TCA. We can make an assumption that if there’s a
lot in the water, then it is likely there is a lot going off into
the air. That’s what we know today.
We knew even less in February 2007. A new Great Wolf Lodge in
Mason, Ohio, had an issue no one could put their finger on. It
wasn’t until we had done a lot of research and testing that
we thought we found some solutions.
None of us knew at the time that these valuable lessons learned
would impact the development of the ventilation module of the Model
Aquatic Health Code.
We knew developing the ventilation module would be a challenge
because the spectrum of indoor aquatics facilities is wide and
water treatment also is needed to include new technologies that are
not in widespread use.
What worked for one facility might be overkill for the other, so we
had to think of how to approach this without adversely affecting
either end of the spectrum. It was apparent we would need a diverse
group to be on the technical committee, so we selected a team of
experts with specific backgrounds: academics, sanitarians,
government specialists in industrial hygiene, facility operators of
varying types of facilities, designers, manufacturers and ASHRAE
We had some very lively discussions on the various aspects of
indoor air quality, then we broke these down into sections so we
could systematically address them.
- Which contaminants are in the air based on peer-reviewed science
- The effects these contaminants have on people, and which contaminant thresholds were already established in current research
- How these contaminants get into the air so we could address the mechanism of entry
- What the hierarchy of design should be (bather comfort vs. building protection)
- Parameters for smaller, low bather facilities with low ceilings vs. high occupancy facilities with huge air volumes
- Requirements for pools with basic water treatment vs. those with sophisticated systems designed for managing contaminants
- How facilities are maintained by on-site staff
- How to address the contaminants brought in by bathers
- How to write a code that would be practical, meet the objective of improved air quality and yet could be enforced by sanitarians
We discussed all the objectives outlined above, but we also had
three distinct conversations about contaminants and thresholds;
fresh air requirements; and the use of UV and ozone to minimize
Very early on in the discussions, we evaluated the known biological
and chemical contaminants present in the air and determined their
prevalence and adverse effect on bathers. The research
pointed to TCA being most prevalent and the compound having the
most well-known adverse effect. But we also had a challenge in
determining what would be an acceptable threshold in an indoor
First, the test method used for TCA in the research varied, so that
meant the amounts recorded could be different among the research.
Second, there is no easy test that a sanitarian or operator could
use in the field that would allow for a real-time test as we have
for testing free chlorine, pH and the like. It would be difficult
to enforce a threshold that could not be easily measured. As a
result, the ventilation module has not proposed thresholds, but as
technology develops for real-time testing, we may be able to
incorporate measurable and enforceable thresholds into future
editions of the MAHC.
As we considered airborne contaminants, we discussed the fact that
under current practices, the most common solution was bringing in
fresh air. This removed contaminants and diluted the amount of
contaminants regardless of the type. We had a “think
tank” session in which a formula for fresh air was
Using ASHRAE requirements as a base, the group developed an amount
of fresh air required to not only account for the building size,
but for the types of pools, and the number of people in these
environments. This helped us address small and large facilities, as
well as low bather vs. high bather load facilities.
The approach was practical, considering the density of people in
pools and the fact that certain pools contribute to air quality
differently. Moving water releases TCA more than flat-water pools.
Hot water releases more contaminants in the water, and evaporation
releases more TCA into the air. The formula used for determining
the minimum fresh air requirements is modular, so it will not limit
Lastly, we discussed the use of UV and ozone as a method to control
combined chlorine in pools and hence remove the precursors to TCA.
The problem is, the types of equipment on the market vary greatly
and how they are installed determines their efficacy. To know
definitively that UV or ozone would be effective, a test method
would be needed to prove the equipment’s efficacy under
certain conditions. Without the research to show the efficacy, we
had to rely on what we know works and could be measured.
As a result, the backbone of the ventilation module is the formula
for determining fresh air requirements. We think this will help
designers plan for fresh air, not just based on the square footage,
but also peak occupancy and type of pools (for example, flat,
agitated and hot water). We believe it is practical and reflects
the standard practices in how water quality is maintained. It also
adds safety factors for air handling based on contamination burden.
We hope you find the same as you read through the document posted
for public comment through June 12 on CDC’s Healthy Swimming Website. Your input and
comments are appreciated and will be considered even after the June