Work environment has been a subjective requirement from the beginning. All you need is a stroy. Well, not a story, but be ready for a discussion.
Fire Girl's discussion is a good example which covers the basics. Auditor's do not walk around with light meters, for example, nor is there definitive criteria in most (99.99%) situations where a light meter would be necessary as a process criteria (as opposed to 'standard' laboratory conditions for which there are many sources of,to say the least, industry standards). If light is a 'critical' issue, the expectation would be they would want to see records of it being monitored.
Don't get excited. Work environment is subjective and relative. A metal turning station, for example, will typically be dirtier than a simple assembly area or a soldering station.
-> Does a simple health and safety seminar would be enough?
That's standard introduction training, isn't it? Has to include MSDS training. Or departmental specific in worst case? This has to be done.
-> certificate?
For what?