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Comment by keypusher | Hacker News Reader

Chlorine reacts with pretty much any organic compound (hair, sweat, skin, urine) to produce chloramine. And yes, while this is the thing that irritates your eyes, it's not to say that chlorine is harmless either. There is evidence for respiratory and organ damage from extended exposure to chlorinated pools.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4351252/

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Be it airborne chlorine or chlormines, it is an air-quality challenge. Facilities need to take pool ventilation seriously, especially ways to draw fresh air across the water surface where chloramines tend to linger (they are heavy). However, getting facilities to upgrade their ventilation is hard: it is a substantial cost and there are very little health and occupational safety regulations. Standard pool inspections do not check air quality; and air-quality inspections are time consuming (4h+) and expensive (>1K). At a societal level, we need to be putting patron and staff pressure on facilities that have ventilation problems and letting others now about these health issues.

Not to mention that good air ventilation close to the pool's surface has the side effect of accelerating evaporation and thus cooling the water, requiring more energy to keep the temperature up...

Putting the exhaust air through a heat exchange unit or dehumidifier can collect most of the evaporated water and lost heat.

Some how I feel this would be very inefficient due to small delta-temp.

> "Unfortunately, one of the rats accidentally drowned during swimming training; therefore, the final animal number of the [experimental group] was 17."

Damn, poor guy.

> "When training, a screw nut approximately 3% of their mean body weight was tied to the top end of the tail of each rat, and all rats were kept in the special pools with water of 60 cm depth (water temperature 25–30°C, pH 6.5–7.0) until fatigued (submerged below the surface for five seconds twice). The fatigued rats ceased training immediately, were removed from the water for a short break, showered with running water and then dried with hair dryers."

So, systematically drowning rats until they aspirate water, every day for twelve weeks. And they showed negative respiratory effects. Huh.

They had a control group that also had the training.

> systematically drowning rats until they aspirate water

We prefer the term "advanced interrogation techniques"

This gives me an idea of an online gambling site where people bet crypto on which rat will drown first. I will call it thunderpool. 2 rats enter, 1 rat leaves.

Place your bets if this cat in this box will be dead or alive when the box is opened at Schroedinger's online casino!

That study seems dubious -- they mention that they measured free chlorine with a DPD test, and they also say that they measured chloramines with a colorimeter and the DPD test. This seems quite odd -- the distinguish between free and combined chlorine (which mostly means chloramines), a better test such as FAS-DPD should be used. So I don't see how the study determined what the cause of the problem was, but it certainly spends quite a bit of time explaining how chloramines can be problematic.

Anyway, chloramines can be controlled to some degree. The use of stabilizers (cyanuric acid) can reduce the amount of nitrogen trichloride (the worst chloramine) in the water by a considerable amount. As I understand it, the factors that make the biggest difference, though, are maintaining adequate chlorination and exposure to UV light. UV light (from the sun or a UV lamp) breaks down chloramines. So the best solution is to swim in an outdoor pool :)

(The FAS-DPD test is a standard test kit you can buy from ay reputable dealer. It's a titration, not a colorimetric measurement, so no fancy equipment at all is needed.)

So basically, if chlorine isn't generating chloramine, then the chlorine is useless to begin with

Yes, which is why it's important to regularly "shock" the pool to oxidize the chloramines, typically by superchlorinating the pool, but much more effectively by adding ozone.

We just got a pool recently (salt-water chlorinator), and the advise out there on how to maintain one is just utter superficial garbage. I'd never heard your statement before, and I thought the shocking was just to keep the right level of chlorine. Seems like all the advice is heavily biased towards just getting your local pool shop to tell you what you need to add!

Your comment on ozone made me do some quick searching, and [0] suggests to me that I should also run my pool pump for longer at lower RPM. I'm interested too in how I can minimise the cost of running the pool, which that will help with.

[0] https://aquamagazine.com/service/ozone-and-uv-systems-allow-...

There is a lot of great information at https://www.poolspaforum.com/forum and https://www.troublefreepool.com/forums/ particularly from user 'chem geek'. This is where I was able to finally get a better understanding of pool/spa chemistry and figure out a routine that works for me.

+1 for troublefreepool.com. Anyone with a pool or spa (hot tub) should read through their 'pool school' section, and then take any questions to the forums. (Probably don't even need to post; every imaginable question has already been asked and answered there.)

As well as shocking when necessary, just keeping a sufficient level of chlorine can help with continuously oxidizing chloramines. Often when you get buildup it's because the chlorine level in the pool dipped too low. In fact, for a residential pool that doesn't normally see large numbers of swimmers, if the chlorine level is kept consistent (somewhere between one and several ppm depending on things like pool type, whether a salt water chlorine generator is used, amount of sunlight, etc.), shocking regularly may not even be necessary. (We almost never shock ours, and with our SWG running at around 20% about 8 hours per day, consistently maintain 1-2ppm free chlorine, and almost zero combined chlorine (chloramines). Again, YMMV depending on a number of factors, but the key is to keep a sufficient free chlorine level (which may mean boosting it up in anticipation of a large swimmer load, such as before a party), and then yes, shocking if it does drop down too low and chloramines spike.

It's extremely helpful to have a decent test kit, like the ones sold by Taylor. The color-change 'strips' are almost worse than useless, as they can often give misleading readings. The info at troublefreepool.com is also very useful when first learning this stuff.

There's plenty of organic compounds within our respiratory tracts and other mucus membranes, so it would make sense that if chlorine gets in there, regardless of whether there's already chloramine in the environment, there soon will be.

Also, chloramine is what gives a pool that "pool smell".

Makes you wonder about outdoor swimming pools (which would equally include water parks) that use chlorine. Given UV breaks it down, it would explain why outdoor pools that use chlorine, tend to have higher levels to counter the increased loss.

Which makes you wonder about exposure, whilst out in the open, the levels of chlorine gas given off would be higher. So a sunny calm day, may well be the case of higher exposure levels than a shaded indoor pool. Equally indoor pools that are exposed to UV sources would theoretically be the worst offenders in chlorine exposure.

I submit that on sunny calm days with no wind at all, an outdoor pool will still get more air ventilation than the vast majority of indoor pools because, despite the absence of wind, you'll still get convection currents in the immediate area of the pool (particularly because the deck will usually get quite hot as it bakes in the sun.)

This may be the same issue as is seen in crop pesticides. The practitioners don’t trust the science and try to play it safe by adding more than is advised.

So safer to use outdoor pools if that's an option.

UVC sterilizers seem like another option I think, not sure how effective that is though, and I'm not sure of the availability of things like this.

It would sterilize water passing through the system, but not maintain ambient antipathogenicity. Typically, a diatomaceous pool filter, pool sweeper (like the old Polaris... the pool Roomba from the 1980's), chlorination and chemistry monitoring are needed.

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