All fields are required.
When it comes to measuring for good indoor air quality and the strategies to employ in pursuing remediation, it really pays to first stop and consider what you really want to achieve.
Consider this from Andrew Persily, leader of the Indoor Air Quality Group at the National Institute of Standards and Technology: "You can spend a lot of money measuring different things, but what are you going to do with the information?" he says. "There are potentially hundreds of different contaminants that could be measured but there aren't established criteria for what's acceptable in non-industrial settings. So unless there's a really good reason for measuring the contaminant and you know what you're going to do with the data, many would recommend against it."
So if it's something obvious, such as you smell mold or you see it, you're probably better off spending your money cleaning it up and addressing the problem that's causing it so you don't get mold again. If all you do is test it without addressing the cause, all you're doing is spending money.
If it's something more subtle than obvious mold, or it's not something clear-cut like cold air blowing on people, it is improper to call a specialist who has only one sphere of expertise. Don't hire a specialist before consulting a generalist.
If workers have symptoms, contact the expert who understands symptoms, how to connect them to the indoor environment, and whom to contact for specific remediation needs.
And even when you have the expert involved, don't permit tests to be performed unless the consultant can explain the results.
Have the expert explain what information the testing will provide and how that information will be used. Again, it's become relatively easy to test for substances. It's not so easy to connect the findings of those tests to human health effects.