A number of applications are based on treatments of food preservation, such as packaging or gasing of vegetables.

For example, gasing of some tuber vegetables (i.g. potatoes) prevents the growth of buds during the stocking period. In some extents, inert gases – which cause asphyxia – can be used, or some waste products produce typical decomposition gases such as methane and hydrogen sulphide.
Grain storage bins and cereal storage areas may produce carbon dioxide. Some fruits may release ethane, carbon dioxide and decomposition materials become dangerous in the nearby areas.
In industrial sausage factories, frozen products are cut by means of nitrogen, therefore they need to be equipped with suitable oxygen detectors to monitor if there are any leaks and safeguard operators' health.

During the production of wines and distillates, the danger of gas comes from the use of substances required for wine preservation, sterilization of tanks or containers, wine fermentation and, finally, stocking of alcohol..

Different additives, such as sulphuric acid, hydrochloric acid and, sometimes, chlorine, are used during the treatment of pulp. In thermal plants fuel, often methane, is used and there is a great amount of hydrogen sulphide in the treatment of backwaters.

Actually, modern thermal plants have almost stopped using liquid fuels. The fuel most frequently used is methane and, to a smaller extent, liquid petroleum gas (LPG).

A lot of chemical processes need gas detectors. One of the most common applications is related to the entrance in tanks for cleaning or maintenance. Usually in these circumstances the levels of oxygen, flammable gas vapours (usually solvents are used to clean tanks), and toxic gases need to be kept under control. A factory, for instance a factory that produces Chlorine, must make use of a Chlorine detector.

Chemical systems can produce final products or products which will be used by other factories in different processes..

Actually, modern industrial kitchens have almost stopped using liquid fuels, but methane or, to a smaller extent, liquid petroleum gas (LPG).

On these premises, the main activity is the first cause of hazard. In fact, if fuels spill out of their containers, they and their vapours represent a top-grade danger of flammability so that they can be triggered off even by the smallest energy sources (spark).

In these particular places, the object of the activity is the most important danger: as a matter of fact, fuel vapours originated during the filling phase are easily (also with a spark) and highly flammable.

In rubbish dumps, due to organic substances decomposition, methane, sulphured hydrogen, and carbon dioxide can be generated. Often, these gases find a way through the layers of ground up to reclaimed areas where there might be buildings.

In these systems the danger is linked to the use of chlorine to purify water. There are many different supplying resources: underground, superficial, or brackish water, if properly treated. In most aqueducts water is disinfected. Disinfection always implies the use of chemical substances (except for ultraviolet disinfection). Chlorine derivates are usually used for this purpose.

In the production of pharmaceuticals chemical substances are used in different conditions and circumstances:

1. In a chemical lab flammable organic solvents are used and stored. These spaces are at high risk of explosion or fire.
2. In the process of preparation of solutions, great quantities of ethylic alcohol may be used. This substance is classified as highly flammable. The use of this substance puts the involved spaces at high risk of explosion or fire.
3. Production of ointments, pastes, creams, and gels: for the preparation of the mass the most used solvents are water and ethylic alcohol. In this phase chemical solvents are used and manipulated for the production of the mass.
4. Usually a thermal power plant has great dimensions. The use of methane creates high risks of explosion.
5. Depending on the type of production, toxic substances can be present.

Besides being substances enriched with Nitrogen, Phosphate and Potassium, the basic material used comes from animal faeces. In their processing, the most hazardous gas is ammonia which develops in big quantities during the first period of seasoning, which often takes place in closed rooms. Like in other places where a decomposition process occurs, the second risk involved here is due to hydrogen sulphide.

Galvanic processes include a so-called “pickling” step where pieces under treatment are polished: this processing makes use of acids. Another process where hazardous substances are used is the degreasing one, where not only pieces under treatment but also production equipment are degreased: trichloroethylene is basically used here.

An obvious application is detection of flammable gases. Danger is there where leaks from the main net or joints require operators to enter narrow rooms for maintenance works. Gas pipelines may leak in areas where operators must enter for maintenance purposes, such as welding, so LEL is to be monitored before any operation.

The big amount of fuel contained in every aircraft make a closed room like and hangar a dangerous place in case of leakage from aircraft tanks.

In plants where foodstuff are produced and stocked, where primary or finished products need to be preserved at a controlled temperature, the most common cooling liquid is ammonia. It is big plants where other fluids would not enable to use such high power.

Crude oil, during the extraction phase, is always rich in light hydrocarbons and often in sulphured hydrogen. Methane does not get wasted, but is collected in pipes to be depurated and distributed.

These applications are usually carried out in the sea and on earth installations. Platforms, perforation systems, oil pipelines terminals, refineries, oil pipelines and transport both during exploration and production, stock tanks, silos, tunnels, and tanks are all at high risk of explosion, H2S and lack of oxygen. Leaks close to valves, flanges, welding works, tanks cleaning and repair process, can be dangerous. Rust on big steel structures indicates a reduction of oxygen, if in limited spaces without aeration possibilities.

In a chemical lab explosive organic diluents are usually used and stored. The use of these substances makes the environment exposed to the risk of explosion or fire. In general these flammable gases are used to catalyze chemical reactions. In other departments one can get in contact with other toxic substances depending on the specific production of the factory. Inert gases that can provoke asphyxia are commonly used.

The heated chemical reaction between pyrite and coal in order to produce steel engenders many risks gas wise. In the blast furnaces coke is used as fuel and releases a highly toxic gas: cokery gas. This gas contains monoxide of carbon, sulphured hydrogen, methane, SOX, and NOX.

The most used gases in therapies and surgery are oxygen and nitrogen protoxide. The first one can be excessively present, either because of a hyperbaric chamber, or because of a leak from the normal distribution system. The second one is a common anaesthetic, which obligatorily need to be supervised in the operating room.

In the underground parking lots with artificial ventilation, toxic or dangerous conditions can be created.

In the production of beer the most considerable gas is carbon dioxide. Besides being a product of fermentation, it is also used to preserve the quality of products. Not to forget that several times fermentation and stocking are carried out in tanks, vats, silos, troughs that need cleaning and maintenance; since they are limited spaces, the operator will have to use a multigas detector.

In the manufacturing process of polyurethane foam and similar substances, pentane is the basic element.

Recharging accumulators of electric drive carriages involves a risk of fire-explosion. In fact, when recharging, the delivery of electric current determines an electrolyse process where hydrogen develops. Also, strong acids contained in the battery evaporate in part. Consequently, the room may be saturated which can form an explosive mix.

In every activity of metallic carpentry or any other activity that needs welding, the presence of flammable gases is necessary. The most used are acetylene and propane and other gases with a different commercial name containing additives for a better performance.

Even when they look clean, tanks can be dangerous; for instance, the presence of water inside might produce corrosion, which will decrease the level of oxygen and produce hydrogen, which is a flammable gas. They might, as well, contain traces of the substance previously used in the tank, or, if they have been cleaned, they might contain the inertizing substance. In conclusion, the safety of the employees can be guaranteed only by using a multigas detector.

Every operation to be carried out underground requires suitable protection and safety devices to safeguard operators from gases that may be there.

In productions of sprays the most common propellant used is propane

During the different manufacture steps, important amounts of hydrogen sulphide may be created which, due to leaks, can create explosive mixtures mainly generated by methane that is normally found in big quantities in this type of activity.

The access to drains and drainage canals is dangerous for the lack of oxygen, methane and sulphured hydrogen. Mud digester: mud digesters can be considered “methane producers” where the crude reflowing water biodegrades producing high levels of methane as a sub product. Normally the 60-70% of the volume is methane, which afterwards will be utilized as fuel for other uses, like electricity production through turbine.

GASES INVOLVED

Flammable gases: different solvents are used to clean machines and matching metals depending on the result required.
Carbon oxide (CO): thermal treatments (metal hardening and tempering) generally take place in carbon-oxide-based controlled-atmosphere furnaces.
Ammonia (NH3): very common substance in “recipes” for thermal treatments.
Methane (CH4): the most commonly used fuel to reach the temperature required for thermal treatments.
Trichloroethylene (C2HCl3): it is an hazardous substance if inhaled and can cause irreversible diseases. One of its target organs is liver.