Gases are an important form of physical presence and are widely distributed in the atmosphere, industrial production and daily life. The properties of different gases vary significantly, determining both their application landscape and safety of use. The following is a detailed description of the core characteristics, typical uses, safety concerns, and the context of the gas detector application, from the common gas classification, to provide a comprehensive reference for industrial operations and daily protection。
Basic atmospheric composition gases: “building blocks” that sustain life and the environment
Such gases are a major component of the earth's atmosphere, essential for ecosystems and human survival, and are stable and widespread。
1. Oxygen (o2)
Physical properties: non-colour-free gases, with a density slightly greater than air (1. 429g/l, standard condition), not soluble in water (1l water approximately dissolved 30ml oxygen), boiling point - 183°c (liquid oxygen light blue), melting point - 218. 4°c。
Chemical properties: strong oxidation, the core gas that sustains combustion and life breathing - - support fuel combustion (e. G., wood, natural gas) to produce co2 and water; participation in human cell breathing that transforms organic matter into energy, oxygen deficiency leads to asphyxiation and excess (>60%) can cause oxygen poisoning (pulmonary damage, central nervous abnormalities)。
Uses: medical first aid (aerobic use by anaerobic patients), industrial welding (aerobic pyrotechnic cutting), aquaculture (aquatic aerobics)。
An oxygen gas detector application scenario:
(a) closed space operations (e. G. Underground mines, tunnel construction): real-time monitoring of oxygen concentrations using portable oxygen detectors to ensure a safe range of 19. 5 ~ 23. 5 % (below 19. 5 % for oxygen deficiency, immediate ventilation or oxygen supply equipment)
Medical oxygen module: installation of stationary oxygen concentration monitors to prevent fires caused by high oxygen concentrations (precipitable burning of flammable materials in pure oxygen environments), while avoiding treatment of patients with low effects at low concentrations。
Safety alerts: flammables (e. G., grease, fabric) in a pure oxygen environment can burn intensely, avoiding exposure of oxygen tanks to open fires and oils; storage away from fire sources to prevent impact leakage。
2. Nitrogen (n2)
Physical properties: non-colour-free gases, slightly less density than air (1. 251g/l), insoluble in water, boiling point - 195. 8°c (liquid nitrogen is colourless and transparent, and heat is intensely inhaled during carbureting), chemically stable (molecular structure n≡n, high key)。
Chemical properties: regular temperatures do not react to most substances and participate in only a few reactions (e. G. Synthetic ammonia, magnesium nitrogen production with magnesium reaction) at high temperatures, pressure or catalyst; it is “inert” and it isolates oxygen from protection。
Purpose: food preservation (filling packaging to prevent oxidation), industrial protection of gas (welding, insulation in the production of electronic components), medical refrigeration (liquid nitrogen for skin refrigeration treatment, cell preservation)。
Gas detector application scenario:
(a) nitrogen protection workshop at the food processing plant: deployment of oxygen/nitrogen composite detectors, with emphasis on monitoring oxygen concentrations (a nitrogen leak dilutes oxygen, triggers alarm when oxygen levels are below 19. 5% and avoids suffocation by staff)
Laboratory liquid nitrogen storage area: real-time monitoring of nitrogen leaks using cryogenic gas leak detector (liquid nitrogen ablution leads to a sudden drop in local temperature while causing a decrease in oxygen content)。
Safety tips: liquid nitrogen has very low temperatures and direct contact with skin leads to freezing wounds; nitrogen leaks in closed space dilute oxygen and cause “nitrogen asphyxiation” (no visible symptoms, pre-ventilation tests)。
3. Carbon dioxide (co2)
Physical properties: non-colour-free gases, 1. 5 times the density of the air (1. 977g/l), soluble in water (1l water approximately dissolves 1. 7l co2 to form carbonate), boiling point - 78. 5°c (solid co2 is "dry ice" and heat is inhaled when heating is raised)。
Chemical properties: non-flammable, non-combustion (except for activated metals such as magnesium), acid gas - - salt from the alkaline reaction (e. G., laboratory use to clarify limewater for co2 deposition); low concentrations are non-toxic and high concentrations (>10%) inhibit respiratory centres。
Uses: food (carbonate beverages, dry ice cold storage), industry (welding protection gas, fire extinguishers), agriculture (concentrating co2 for light cooperation)。
Gas detector application scenario:
Underground warehouses / cellars: installation of stationary carbon dioxide detectors ( high co2 density and easy to accumulate in low-lying areas) to alert the police when concentrations exceed 1% to prevent persons from vertebrates and comas due to oxygen deficiency or co2 poisoning when entering
(b) large shed cultivation: the use of portable co2 detectors to monitor concentrations on a regular basis ensures a suitable range of 800-1500 ppm (too low-impact light co-operation, which can cause crop leaves to be yellow)。
Safety tips: dry ice rises to generate large amounts of gas and storage in closed containers may cause explosions; high concentrations of co2 are heavier than air and tend to accumulate in low-lying areas (e. G. Cellars, wells), which require ventilation and detection of concentrations prior to entry。
Ii. Gases commonly used in industry: “functional gases” driven by production
Most of these gases are used in industrial manufacture, energy supply and are partly flammable or corrosive and require strict control。
1. Methane (ch4, main component of natural gas)
Physical characteristics: non-colour-free gas (commercial gas odour-added agent for leak detection), density is only 0. 55 times (0. 717g/l) of air, extremely insoluble in water, boiling point - 161. 5°c, the simplest organic compound。
Chemical properties: flammable gases with an explosive limit of 5% to 15% (a mass fraction in air), blue flames when burned, co2 and water (ch4+2o2 = co2+2h2o), non-toxic, but leaks cause oxygen-deficit asphyxiation。
Uses: civil fuels (gas stoves, water heaters), industrial energy (power generation, heating), chemical materials (synthetic methanol, ethylene)。
Gas detector application scenario:
Civilian kitchen / gas boiler room: installation of a domestic gas alarm (detection of methane) that triggers acoustic light alert at concentrations of 10%-20% of the lower limit of the explosion, while connecting to cut the gas valve door
(b) along the gas pipelines: deployment of fixed-form flammable gas detectors to monitor leaks in real time (light methane density, high-level detectors) to avoid explosions caused by leaks。
Safety alerts: use in closed spaces is strictly prohibited and gas alarms are required; air is immediately ventilated in the event of leaks, and switch switches or open fires are prohibited (to prevent the detonation of electric sparks)。
2. Acetylene (c2h2, electrophyl gas)
Physical properties: non-colourous gases, pure tasteless, industrial-grade products which smell of garlic because of impurities and have a slightly smaller density than air (1. 177g/l), microsolvable in water and acetone (industrially commonly stored acetone dissolved acetylene in steel bottles to prevent decomposition of explosions)。
Chemical properties: highly flammable, explosion limit wide (2. 5 ~ 82 %), very high combustion temperature (over 300°c for aerobic pyrotechnics), capable of producing explosive compounds (e. G. Acetylene) in reaction with metals such as copper, silver, etc.; chemically active, capable of being involved in the reaction (e. G. Synthetic vinyl chloride)。
Uses: metal welding and cutting (high temperature melting metal for aerobic pyrotechnics), organic synthesis (manufacturing plastics, rubber)。
Gas detector application scenario:
Welding workshops: use of portable flammable gas detectors (targeted detection of acetylene) to monitor concentrations in real time before and during operations to avoid blast limits (with particular attention to poorly ventilated corners, acetylene prone to detention)
Acetylene cylinder storage area: installation of fixed blast-proof gas detectors with acoustic light alarm device, immediate evacuation of staff and ventilation measures as soon as leakage is detected。
Safety tips: storage of cylinders is required to avoid a violent impact and is prohibited from contact with copper-making equipment; when used, it is used far from the source of the fire and the flow speed is controlled to prevent a return to fire (reventors are required)。
3. Ammonia (nh3)
Physical properties: non-colourous gases, strong irritant odour (like urine), density 0. 771g/l (lighter than air), highly soluble in water (1:7000 volume ratio, resulting in ammonia, alkaline), boiling point - 33. 5°c, liquid (repression or cooling becomes liquid ammonia, used as a refrigerant)。
Chemical properties: alkaline gases, with acid reaction producing salts (e. G., ammonia in contact with hydrochloric acid to generate white smoke and ammonium chloride); more stable at constant temperatures, which can be decomposed to nitrogen and hydrogen at high temperatures; and no (for industrial nitrate)。
Uses: agriculture (manufacturing nitrogen fertilizers such as urea, ammonium carbonate), industry (refrigerant, surface treatment of metals), medical (sream water for skin disinfection)。
Gas detector application scenario:
(a) fertiliser ammonia synthesis workshop: deployment of stationary ammonia detector (amino irritating and dispersible) to prevent respiratory irritation of persons by alerting the population at concentrations above 25 ppm (tlv-twa, time-weighted average threshold)
Refrigerator (amino-refrigeration system): installation of blast-proof ammonia leak detector, with emphasis on monitoring pipeline interfaces and valves, triggering alarms as soon as leaks occur, while connecting to cut off the refrigeration system and avoiding explosions caused by the mixing of ammonia with air (15% ~ 28% ammonia explosion limit)。
Safety alerts: irritated odour stimulates eye, nose, and respiratory tracts, with high concentrations (>30%) leading to chemical burns; leaks require a reverse wind evacuation and wash with fresh water immediately after contact with skin; storage avoids mixing with acids。
Toxic and hazardous gases: “hazardous gases” requiring priority protection
Most of these gases originate from industrial leakages, incomplete fuel combustion or biodecomposition, and are highly toxic to humans and require strict monitoring and protection。
1. Carbon monoxide (co)
Physical properties: non-colour-free gases, density close to air (1. 25 g/l), insoluble in water, boiling point - 191. 5°c, chemically unstable (reactive to oxygen, metal oxide)。
Chemical properties: highly toxic gases - the ability to bind to human haemoglobins is 200 - 300 times greater than oxygen and forms “carbon oxyglobins”, resulting in the failure of haemoglobins to transport oxygen, causing tissue oxygen deficiency (light poisoning: headaches, nausea; severe poisoning: coma, death); flammable, flammable, 12. 5 ~74. 2 %, burning to produce co2。
