By The Zagosa Team. Published .
Reviewed or updated .
Chlorine and bromine both have a scent, but the two are worlds apart. Chlorine reads sharp and chemical. Bromine is gentler, a little sweet, and far less penetrating. The reason comes down to the by-products each leaves behind once it has dealt with organics.
What your nose is actually picking up
With chlorine, the smell you notice is rarely the chlorine itself. It is chloramines, the compounds chlorine forms with sweat and body oils. Chloramines are volatile and irritating.
With bromine, the equivalent compounds are bromamines. These are still active sanitisers (unlike chloramines, which are basically spent chlorine), and they are far less volatile. Less volatile means less smell.
What each scent signals
A strong chlorine smell nearly always means chloramines have built up and the water is due a shock. The free chlorine reading will usually be lower than you expected.
A strong bromine smell is rarer and usually just means the level has drifted above 8 ppm. Take a couple of bromine tablets out of the feeder for a day and the level settles naturally.
A neutral, faintly fresh scent from either one is what you are after. If you cannot smell anything at all, also check you have not simply run out of sanitiser.
Why hot tub owners often lean to bromine
Indoor or partly enclosed UK setups build up smell faster because the gases cannot vent. Bromine is much kinder in those spots.
Sensitive noses (often the same households with sensitive skin) find bromine far more pleasant to be around.
Regular gatherings: if you often host friends in the tub, bromine's lower smell signature keeps the chat off the subject of chlorine complaints.
Common questions
Is one safer than the other?
Both are safe at the recommended levels. The difference is by-product comfort, not safety.
Can I tell which sanitiser a tub uses from one sniff?
With a bit of practice, yes. The sharp, eye-irritating smell is chlorine plus chloramines. The softer, slightly sweet one is bromine. The cleanest smell of all is a well-balanced tub of either.