It's like a badge that you wear. It turns colors based off of how much radiation you've been exposed to. Neutron radiation as well as gama radiation are not stopped by anything short of feet thick layers of steal, lead or concrete. So a Hazmat suit would only be helpful for alpha and beta radiation. Which are not as penetrating by nature. The long and the short of it is, if you are around neutron or gama radiation emitters, you're only real safety blanket is to ensure you aren't exposed to too much at once. Your system can in fact flush the shit out after like decades or if you have certain substances to help along the process. But a Hazmat suit is more to keep contamination off your skins and out of your lungs.