If you’ve been using laptops for a while, you might have heard about the dangers of laptops burning your thighs. If you have, you’ve probably also heard about the Swedish guy who suffered burns to his penis. When I reviewed my employers’ recent draft “computer use” policy, I noticed the laptop section was missing a section on laptop heat.
So I had a look at the available medical research. And there isn’t much. There is one 2004 study which found that skin burns will occur over a period of 8 hours at 42.5 Celsius (108.5 Fahrenheit). There was the 2008 case of a 24 year old male suffering a 8×3 cm burn on his right thigh. He had fallen asleep while watching a movie. Six hours later, he woke up with a deep second degree burn. And there is the case of the Swedish chap with the burnt penis.
I decided to run a test, to see what heat a laptop generates. And I thought it would be interesting to look at the differences between the various Windows versions.
The test rig: 
Dell E4200 Laptop, towel, PassMark BurnInTest software
Highest temperature seen: 60.3 Celsius / 140.54 Fahrenheit
Temperature under the towel
This was measure by placing the temperature sensor under the first layer of a towel. The laptop was then run until it reached an operating temperature.
| Celsius | Fahrenheit | |
| DOS | 37.9 | 100.2 |
| Windows XP SP3 | 38.6 | 101.5 |
| Windows Vista SP2 | 39.4 | 102.9 |
| Windows 7 | 37 | 98.6 |
Fan exhaust port temperature
This was measured by placed the temparture sensor outside the fan exhaust port.
| Celsius | Fahrenheit | |
| Windows XP SP3 | 42.3 | 108.1 |
| Windows Vista SP2 | 45.2 | 113.4 |
| Windows 7 | 43.2 | 109.8 |
Differences in operating systems?
No as much as I thought. I was expecting Vista and Windows 7 to be cooler than MS-DOS and Windows XP, as they have later technology (power/thermal management) built right in.
About that 60.3 Celsius measurement you mentioned earlier?
I had the laptop resting on a blanket, which was resting my lap. My lap felt warm, so I grabbed the thermometer. 60.3 Celsius!
Further reading
2002: The Lancet – Lap burn due to laptop computer
2004: Journal of Burn Care & Rehabilitation – Temperature threshold for burn injury: an oximeter safety study.
2008: Journal of Burn Care and Research – Thigh Burn Associated With Laptop Computer Use