The reporting does seem confused. It says two staff members were taken to hospital after falling ill, but Edinburgh Council says they were taken as a precaution which implies though doesn't state they weren't ill.
So were they actually experiencing symptoms, and if so, what were they? That's surely in the public interest.
I suppose it’s possible the substance caused some temporary irritation or made them feel unwell without being dangerous, much like, say pepper spray and various other substances can do.
It’s also odd that they haven’t said what the substance was, given that it has now been tested. In similar cases, it often turns out to be something completely harmless, such as talcum powder.