We don't have to go down this road again do we? :
:
Back to the subject in hand...
I've revisited the school this afternoon and re-treated the general area where the problem was.
Used a colloid which shall remain nameless coupled with an odour neutraliser which shall remain nameless, mixed up a bit stronger than for general use. Sprayed generously, brushed in with a rotary, lightly re-sprayed and brushed in again, all over about a 30-40 minute period. Then rinse extracted, partially dried off, re-applied the solution moderately and bonneted to finish.
Smelled fresh as a daisy as I walked out. I'm popping back in with some fans tomorrow afternoon when I've finished the job I'm doing, as I'm anxious to get the area ventilated properly after the extended drying that it will be going through overnight.
I think that may have been part of the problem, the rooms have no decent ventilation so the drying after the first time they were cleaned may have been long enough for bacteria growth to get kick-started.
The other part of the problem may be that I didn't re-apply solution and post-bonnet those areas when I cleaned them initially. I only remembered that today - the reason I didn't post-bonnet is because they were the head & bursars offices where the kids "who cause all the muck" don't go, therefore they shouldn't have needed it :
Hopefully that's cracked it! I suppose I won't really find out until the end of next week.