Burning Time
Burning time is the maximum time to stay unprotected without receiving sunburn. This is calculated from the UV energy equivalent of 1 MED as the basis.
MED: Minimal Erythemal Dose - Is the effective UV dose that causes a perceptible minimum reddening/tanning of previously unexposed human skin. The exact energy equivalent differs by a factor of 2 depending upon individual sunburn sensitivity.
Each value given in each of the categories represents an approximate mid-point value for a range. In the monthly solar reports the sensitive group appropriate to Category 1 is used with a MED of 200 J m-2 effective.
| What Skin Type Are You? | |||
| Category | People covered | Approximate MED | |
| Category 1: (burners) | most UK indigenous groups |  | < 300 J m-2 effective |
| Category 2: (tanners) | mostly non-UK indigenous and non-naturally pigmented groups |  | 600 J m-2 effective |
| Category 3: (naturally brown) | mostly Asian and middle and south American groups |  | 800 J m-2 effective |
| Category 4: (naturally black) | African and Caribbean groups |  | 1000 J m-2 effective |
Source Health Protection Agency
See also global solar UV index at WHO
