In hazard assessment, you prioritize the most difficult-to-detect and potentially most widespread risk first, so you can protect responders and prevent spread before moving on to other hazards. Radiological hazards fit that priority because they can contaminate surfaces, equipment, and people and aren’t always obvious without specialized instruments. Decontamination and shielding requirements are also distinct and time-consuming, so ruling out or confirming radiological risk early keeps the scene safer as you proceed. Once radiological risk is addressed, the next concern is biological hazards. These can be invisible and may have incubation periods, so it’s important to control exposure and prevent transmission before handling other hazards. With radiological and biological hazards addressed, chemical hazards can be managed using established chemical PPE, monitoring, and decontamination procedures, which are more straightforward once the other hazards aren’t a factor. So the sequence radiological, then biological, then chemical reflects the aim to minimize exposure and ensure safe progression through the response.