Convert between radiation dose units.
1 Sv = 1000 mSv = 100 rem. 1 Gy = 100 rad. For photons, 1 Sv ≈ 1 Gy (quality factor = 1). Annual background: ~3 mSv. Occupational limit: 20 mSv/yr. Acute exposure > 1 Sv causes radiation sickness. > 4 Sv is potentially lethal without treatment.