While it was still being investigated, Norris believed the man had likely put the chlorine into a vessel, possibly a bucket, before putting in the water.
If that happened, it would cause a chemical reaction, akin to a "boof", and leave the person slightly injured.
"We've got somebody at home who has mixed some pool chemicals incorrectly, so they've had a bit of an oopsy.
"The chlorine reacts if you mix it wrong so he's had a small chemical burn."
He said incidents of people mixing their pool chemicals in the wrong order was quite common.
"It's pretty common actually ... you've got to put your chemicals in your water because it relies on a dilution process.
"If you put your water in your chemicals it can cause a reaction before you've got enough water in it.
"I'm pretty certain that is what he has done."
Norris said ideally you would have a bucket of water and then put your chemicals in it otherwise the concentration is too strong, "and you end up with a problem".
The man was being treated by St John Ambulance staff, and fire crews were tidying up the scene.