Sunday, 21 June 2015

'Don't put your laptop on your lap!'

I recently read an interesting post from the 'Life of MDW' blog here, which was about why you should NOT call a notebook a 'laptop'.

When I worked at RM (which sold computers to schools), we always called them notebooks, however, despite this, the teachers always called them laptops!

Note: The most common causes of notebook damage were: 1) picking a notebook up by holding the screen and gripping the display too tightly and cracking it, 2) notebook falling off a chair\sofa\lap whilst on, 3) sitting on it when in a bag (often damage was caused by the UK three-pronged mains plug pressing into the screen lid).



We tried to discourage customers from thinking of them as 'laptops' for the following reasons:
  1. Resting a notebook on your lap is just asking for it to slip off and be dropped onto the floor. It may not cause any physical damage to the case or screen, if you are lucky, but it probably has harmed your hard drive and may lead to data loss in the future.
  2. The ventilation grills can be blocked by your legs/trousers/skirt. This can cause the notebook to overheat. The fan will also have to work harder and this will reduce the battery session time if not connected to the mains supply.
  3. The heat may be too hot for comfort on your legs (especially if the ventilation grille is blocked)
  4. If the notebook runs at a hotter temperature, the notebook battery will get a lot warmer. This significantly shortens the longevity of the Lithium Ion battery (that is why you should never keep your smartphone in a warm pocket or exposed to warm sunlight all day!).
  5. Microwave radiation (read below)
Modern notebooks have WiFi and BlueTooth and these radiate 2.4GHz microwaves (the same frequency used by microwave ovens that heat water molecules)! Some of our first WiFi-enabled notebooks had manufacturer warning labels on them saying not to place any part of your body within 10 cms of the rear of the case, where the aerials were located. That little notice caused many teachers and parents cause for concern about cancer and other health concerns and resulted in 100's of calls to our support lines!

Note that problems are caused just by the heating effect of the microwave radiation, rather than any ionising effect. For example, sperm is known to be less 'virile' at warmer temperatures (which is, of course, why a man's gonads are on the outside of his body!).

The WiFi PCB in a notebook, however, is often located underneath the notebook base unit, and placing the notebook on your lap means that it is probably less than 1cm away from your flesh and quite near to your gonads!

It is true that notebooks do have some electromagnetic shielding, but I have seen many where there is very little (if any) shielding around the WiFi card, as this part of the notebook is not considered to radiate 'unwanted' frequencies which could cause EMC interference.


Have you ever used a notebook which was resting on your lap and felt an uncomfortable 'burning sensation' on your leg? If you feel the underside of the notebook, it is usually only just warm and not very hot. Try turning off the WiFi and bluetooth and see if the burning sensation stops. The 'burning sensation' is probably caused by the microwaves heating the water in the cells of your flesh! I sometimes use a 2cm thick 'tray' of wood on my lap to rest my notebook on, and I still get a burning feeling on my right-leg unless I disable the WiFi in the notebook.

So,  I suggest you and your children always use a notebook on a flat surface that is at least 10cm away from the more 'precious' bits of your body! (i.e. use a desk or table!) - and always refer to them as 'notebooks' and not as 'laptops'.

These concerns also apply to other WiFi devices, such as Tablets, Smartphones and Bluetooth headsets.  In the case of a Bluetooth headset for my Smartphone, I only wear mine when really necessary and I use a hands-free set up in the car. Having a microwave source right next to my brain all day is not a good idea!

Note that electromagnetic radiation obeys the Inverse Square Law. If a notebook's WiFi PCB card is 1cm away from your body, you are receiving 100 times more radiation than if it was 10cm away from you (and if 1mm away, then 10,000 times more!).