I used to put a citrus booster into my detergent prespray, but it was mainly to hide the horrid smell of the detergent!
In two years of using m-power and microsplitters, I've had ONE issue with the smell.
The callback was from a doggy house with wool carpets, where in retrospect I should have used a deodoriser anyway. To rectify, I simply sprayed back over with a mixture of m-power and odour neutraliser and whipped a bonnet over it quickly.
I think since dropping the detergents, the vast majority of my regulars appreciate the fact that they're not choked out of their own homes when the carpets are cleaned and like the different approach. I certainly do too, I shudder when I think about all that crap I used to breath in, my citrus-smelling booster isn't a very eco-friendly product so I'm sure it's not good for you :
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If you feel you need to leave a fresh smell behind, carry a trigger sprayer on your van with some smelly stuff mixed up in it. Simply squib a bit round in every room at the end of the job. After a while you'll get used to the lack of smell and probably stop doing it