After working in air fed suits,operatives are required to give samples from their nasal passages by blowing their nose into a tissue,which is then counted in a noseblow counter. How does this work?
The big risk for people working in the nuclear industry is if they breath in particles of anything that emits alpha particles. The problem is that the dust particles lodge in the lungs and sit there pumping alpha particles into the surrounding lung tissue, which eventually becomes cancerous. By contrast contamination on the skin will be washed off, rubbed off or just fall off as the skin cells are shed.
Your nose contains filters to remove large particles of dust, so if you've breathed in contaminated dust there's a good chance some will have lodged in your nose, and of this some will be expelled when you blow your nose. So if you blow your nose and the expelled mucus contains contaminated dust you're in trouble and need treatment immediately.