Curiosity corner
Did you know?

BSI lists at least 7 different methods of determining flash points, and others are in use, or are still sometimes quoted in safety datasheets. No they don’t all give the same answer, flashpoint results are significantly influenced by the test method. Just to add to the confusion, we now also have a test for explosion point (BS EN 15794), which is similar, but different. Its relevance to safety assessment is very limited, but others in Europe wanted this standard.

Use the results with caution.

The American firm Rodex used to market equipment designed to inject propane/oxygen mixtures into rabbit burrows and ignite the gas, as a way of killing the animals. It was never clear how you were supposed to avoid blowing up the ground you stood on. They filed for bankruptcy in 2003. A similar product is still marketed by Meyer industries in the USA.

Customs inspectors assume that on average, 1% of the contents of a maturing whisky barrel is lost by evaporation every year. From a single warehouse this amounts to 10s of tons of alcohol each year. What a waste!

Polystyrene foam is made from heating up beads soaked in pentane. These beads, impregnated with blowing agent are manufactured in bulk and sold around the world and have their own UN code number 2211. They are packed in cardboard boxes (octabins), from which some of the pentane is expected to evaporate. It is the only example of dangerous goods sold in packaging that is designed to leak. There have been incidents where the gas has accumulated in a freight container, and been ignited when the container is opened.

Hydrogen is very easily ignited by an electrostatic spark, but just how sensitive it is was illustrated by an explosion at a factory refurbishing lead acid batteries. An old label was torn off the casing of a battery, and hydrogen which had leaked through a crack ignited. The explosion tracked back into the battery which exploded. This is the fuel of the future.

Although the requirements for a hazardous area classification in DSEAR only dates from 2002, there was a British Standard Code of Practice on this as far back as 1964 (BS CP 1003). UK Legislation requiring special electrical equipment where explosive atmospheres can form goes back to the 1908 Electricity Regulations.

Before ATEX and DSEAR, there was a scheme for zoning dusty areas in the UK with letters for the zones, but this was never widely used. In Germany the dust zoning scheme defined zones 10 , 11 and 12

Early experimenters trying to make an internal combustion engine used coal dust as a fuel, before petroleum products were easily available. It proved much easier to make a carburetter for liquid fuels. Small scale dust explosions are not easy to produce repeatedly.

The heat released from burning one gram of aluminium power is at least 6 times more than the energy released from exploding one gram of TNT. The flame temperature of an aluminium dust explosion is limited mainly by the vapourisation temperature of the oxide.

Otto fuel is a stabilised blend of propylene glycol dinitrate, used for many years as the propellant for torpedos. American data on this blend suggests it has a flash point of 130 degC, but an autoignition temperature of 121 degC. This paradox, that suggests it can fail to flash in a flashpoint apparatus, at a temperature above its autoignition temperature seemingly is a result of the liquid starting to self heat from 121 degC, while it actually ignites at some higher temperature. Self heating like this is much more common with dusts, that start to decompose or smoulder at one temperature,while in sufficient quantity can progress eventually to flaming combustion at some higher temperature.

Manufacturers of firelighters were once given dispensation by HSE not to mark their products as flammable solids, seemingly on the basis that they were articles and not a substance. Would anyone want to buy a fire lighter that did not meet the description that applies to UN class 4.1 (a solid that is readily ignited, and once ignited continues to burn vigorously)? Would hazard labelling put you off buying them? Thankfully common sense later prevailed.

Old habits die hard. Much electrical equipment in hazardous areas in the USA is connected through metal conduit, while Mineral Insulated Copper Clad cable is used in Europe. This system dates back to the time when gas lights were being ripped out, and the gas pipework provided a convenient route for threading the replacement cables without damage to the ceiling or walls.

Spontaneous human combustion may sound like something out of a horror movie, and the idea is certainly horrific. Stories of it happening, however, spread over many years, and some are quite well documented. They tend to have in common a slow process that leaves only the extremities untouched, and is most likely to occur with people who are overweight.

There’s quite a good review in Wikipedia here

See also on the site
The well respected names of Prof Dougal Drysdale, and from the USA John de Haan have evidently thought it worth some limited research effort. Their conclusions are not clear…………..

My view: if you are seriously fat, don’t risk falling asleep close to a strong source of radiant heat.

A little wisdom from a very simple source:
Eeyore whispered back
I’m not saying there won’t be an Accident now, mind you. They’re funny things, Accidents. You never have them till you’re having them.