You need to be careful, when you talk about "Industry Standards", one major PLC actually sells 3 different "Standards" of cleaning to the more price concious customer!
In my opinion these so called standards are quite impossible to work within, unless the building concerned is a "Standard" office building(What that exactly is, I don't know

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We work to Standard Times, which is not the same thing, what I mean by this, is over the last 20 odd years, we have built up a database of the times it takes to clean various items, area's etc, then we make a personal judgement on the density/use and traffic within those area's, then we can estimate the time that building will take to clean, it is very rare that we get it wrong!
Also the clients requirements, must be taken into account, after all a thorough clean right through any building will take longer, than a contract that states its purpose to maintain an acceptable level of cleaning throughout said building, hope this helps.
Regards,
Rob