Liquid gas vapor is heavier than air, and this property is important for safety. Leaking gas settles near the ground and concentrates in lower places, making its dissemination more difficult. Therefore, liquid gas must never be stored or used underground.
Like public network's natural gas, liquid gas is totally odorless; however, an odorous substance (ethyl-mercaptan or dimethyl-sulfide is added to it, to help detect the gas via the smell, in concentrations smaller than 1/5 of the minimum ignition threshold) before it is distributed to the market, in order to facilitate leakage detection.
However, in some cases where the odorous substance is harmful for a certain production process or does not serve as a warning, no odor is added to liquid gas (odorless gas is used, for instance, as a propellant).
Liquid gas is flammable in the air and, even though it is not toxic, in large quantities it can cause asphyxiation. Due to the quick vaporization of the liquid phase and the consequent drop of temperature, liquid gas can cause serious injuries if it gets in contact with human skin. Handlers must use protective equipment, such as gloves and goggles, in case they are exposed to such harmful conditions.
Liquid gas is a high-efficiency fuel, but it ignites only when mixed with air in an analogy of liquid gas to air between 1:50 and 1:10 (this threshold is lower than the equivalent for natural gas). A low ignition threshold means that even small leakages can have serious repercussions. The ignition of this mix is comparative to an explosion when it takes place in a confined space, because of the rapid emission of thermal energy (abrupt expansion of the air - gases). When the mixture of liquid gas and air is outside the limits mentioned above, it is either too poor or too rich to ignite. A leakage of a relatively small quantity of liquid gas can create a large volume of gaseous state and consequently a large volume of ignitable mixture. In order to check the presence of liquid gas in the air, and most importantly an ignitable analogy, special instruments for the detection of ignitable mixtures are used.
The temperature of liquid gas ignition in the air is around 500° C, lower than the corresponding temperature for natural gas, but more energy is required for the ignition.
The energy value of liquid gas is approximately 2,5 times higher than the one of natural gas, which means that more energy is produced by the same quantity of gas.
Liquid gas is chemically potent and causes damage to natural rubber and certain plastics. Liquid gas must be used exclusively with equipment and devices designed especially for it.
