A 10 OR 15 MINUTE SESSION IN A BED IS EQUIVALENT TO HOW MANY HOURS IN THE NATURAL SUN?
There is no formula for relating indoor tanning times to outdoor tanning times because the sun’s strength and spectral (UVA/UVB) output varies with time of day, time of year, latitude, elevation, cloud cover, pollution and reflection. You should mention, however, that the sun’s average UVB output on a summer day in California is 80%, compared to 2-4% in the beds.
