Mills are fabulous buildings; however, they are also incredibly fragile, and unfortunately they sometimes suffer huge disasters.
Windmills, like other tall buildings such as churches and skyscrapers, are particularly susceptible to lightning damage. In particular, iron sail rods on shuttered sails can attract lightning and in patent sails electric charge can pass down to the sack chain and in some instances these have been welded into a solid stick.
Lightning is caused by a polarised thundercloud with a positive electrical charge in the upper section and negative in the lower section, whilst the earth has a positive charge. This also works together to build up to an electrical charge of up to 100 million volts. Lightning forms as a way of passing this current between the different charges as a way to rebalance the charges. The air around lightning strikes can get to five times the heat of the sun. This causes the air to rapidly expand and vibrate which leads to what we hear as thunder.
If a building like a mill is between the path of a lightning strike and ground immense damage can be caused. To avoid damage, windmills make use of lightning rods to provide a low-resistance route to the ground.
Mills are highly flammable buildings. Fire can cause immense damage to traditional mills as well as more modern roller mills. This can be caused by flames such as cigarettes and candles as well as the build-up of friction between millstones or roller machinery if incorrectly used.
Flour dust is particularly susceptible to catching fire. This is because flour is made up of starch which consists of chains of sugar and sugar burns very easily. Indeed as flour dust is very small flames can flash through a dust cloud very quickly causing a flour explosion. It only takes 1-2 grams of dust per cubic foot to be ignitable, and the more finely it is ground the lower the energy required to ignite the flour. In fact the energy required can be as low as the static energy produced when taking off a jumper. Meaning millers have to be very careful to avoid a flour explosion which can be incredibly dangerous.
Tail winding occurs when a windmill is caught with the wind blowing to the rear side of sails. This can happen if the fantail is not working correctly or in the case of a mill without a fantail, if the miller has been unable to turn the mill appropriately to the wind experienced. This has the risk of reversing the rotation of the mill, at best this can cause minor damage at its worst this can result in the cap of a mill or the sails being blown off.