Alpha particles are stopped by a sheet of paper or the outer layer of skin; beta particles by a few millimetres of plastic or aluminium; X-rays and gamma rays have no fixed range and are reduced exponentially by dense, high-atomic-number materials; neutrons are slowed by hydrogen-rich materials such as water, polyethylene and concrete.
Reviewed 2026-09-24
Penetration at a glance
How far each radiation penetrates
- Alpha particles stop in a sheet of paper or the outer skin.
- Beta particles stop in a few millimetres of aluminium or plastic.
- X-rays and gamma rays are reduced by lead and other dense materials, but never to exactly zero.
- Neutrons are slowed and absorbed by water, polyethylene or concrete.
Each radiation needs a different barrier
| Radiation | Typical barrier | What to watch |
|---|---|---|
| α | Paper, skin, a few cm of air | Harmful mainly when inhaled or ingested (internal exposure) |
| β | A few mm of plastic or aluminium | High-energy beta in heavy metals produces bremsstrahlung X-rays, so low-Z material is placed first |
| X / γ | Lead, tungsten, bismuth and other high-Z materials; thick concrete | No fixed range: intensity falls exponentially and depends on energy |
| Neutron | Water, polyethylene, concrete; boron-containing absorbers | Capture can produce secondary gamma rays that also need shielding |
What this means for product selection
X-ray and gamma shielding products are designed and tested for photons. Their ratings say nothing about alpha, beta or neutron protection, and each field needs its own evidence.
References
- IAEA — Radiation, People and the Environment (2004)
- 新莱福防辐射产品手册（2024-09 V1）科普章节
This encyclopedia is for general and engineering reference and is not medical advice. Consult radiation protection or medical professionals for individual exposure assessment.