With oil-based stains and finishes, reading SDS safety sheets makes it clear that safely using the products requires nitrile gloves, serious ventilation, and a respirator that can handle VOCs.
With water-based stains & finishes, safety lines are more blurred.
Most SDS safety sheets for water-based stains classify their products as non-hazardous substances (but still say to use gloves/ventilation/respirator).
Some water-based finishes are classified as hazardous substances by their SDS, like Minwax Polycrylic. Other water-based finishes are listed by their SDS as being non-hazardous, like Varethane Water-Based Polyurethane and General Finishes High Performance Water-Based Topcoat
For water-based stains & finishes listed as non-hazardous, what is the real situation with safety? Can I brush this stuff on indoors without a respirator? What about with a respirator, but no/little ventilation? Is an open window considered enough ventilation? If there is practically no odor during or shortly after, am I still inhaling VOCs that are harming me & my family?
*Edit I should specify that this question specifically refers to brush application
Best Answer
I worked in a lab, so SDS sheets and I are good friends.
Non-hazardous materials have SDS sheets all the time. My favorite SDS sheet is [that of water][1].
You'll note that the "symptoms and effect" of water (a non-hazardous material) states "Not expected to present a significant hazard under anticipated conditions of normal use."
That's not the same thing as "water is safe" (as it kills thousands each year.) It means that one doesn't expect unanticipated danger from handling water.
What's an anticipated danger? Well, it is dependent on context. Lack of ventilation in an enclosed space is an anticipated danger within the painting world. Extreme skin contact for prolonged periods of time will probably cause skin irritation too.
Ventilate properly. However, respirators are not necessary, because using a respirator to paint is an additional safety precaution, and a non-hazardous material doesn't require additional precautions. For those who play it "better safe than sorry," they can use their non-needed respirators, assuming they've already handled the standard precaution of adequate ventilation. One type of safety doesn't replace another.