Emergency services were called out to reports of a chemical incident at Glenwood High School on Saturday.

They discovered that a member of staff had accidentally mixed chemicals used for cleaning the swimming pool.

That pool chemicals are extremely dangerous is so often forgotten. I have come across numerous incidents of explosions, vapor discharges or wild, out of control reactions due to the mixing of different pool chemicals. Possibly the most frightening and perhaps the easiest mix to “accidently” make is the combination of dichlor and calcium hypo with some water added to it.

In pools where the chlorine needs to be predissolved and the pool operator mixes some dichlor and cal hypo in the same bucket, the resulting explosion and thick pungent cloud of yellow “mustard gas” is horrifying to witness. The gas explodes upwards in a typical mushroom shape. Thankfully, people unfortunate enough to be nearby when it all goes bang generally remain below the cloud of gas.