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Dräger's Guide to Portable Gas Detection - 36 Pages

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Dräger's Guide to Portable Gas Detection
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Catalog excerpts

Drager. Technology for Life

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Gases – what is Gaseous Matter? Matter with a temperature above its boiling point is said to be a gas. With respect to a human environment (normal conditions), any substance with a boiling point below 20°C at normal pressure is a gas. The lightest gas is hydrogen (H2, fourteen times lighter than air); the heaviest gas (about ten times heavier than air) is tungsten hexafluoride (WF6). Under normal conditions, 1 cm3 of gas contains about 30 trillion molecules. The average distance between each of these molecules is only about three nanometers. They swarm through space at some 100 to 1000 meters...

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Vapors – aren’t they Gases too? Unlike gases – of which there may be only 200 to 300 – the term vapor is used for the gaseous state of matter below its boiling point. Vapor always exists in equilibrium with its liquid (sometimes also solid) phase – it condenses and evaporates depending on the temperature. This behavior is best recognized in water: The cooling of humid air at nighttime causes fog (condensation) – but the warmth of the morning sun dissolves the fog again (evaporation). In a closed vessel, the maximum vapor concentration always occurs above the surface of a liquid. This concentration...

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Our Atmosphere While continuously decreasing its specific weight, our atmosphere extends far into deep space. The sky’s blue color is caused by scattering sunlight on air molecules (mainly nitrogen and oxygen). The sky is actually already black at a height of about 21 km. If the atmosphere was maintained at a constant pressure of 1013 mbar, its height would be 8 km and the UVabsorbing stratospheric ozone layer would only be 3 mm thick. Typical composition of the earth’s atmosphere in ppm: Gas Main gases N2 – Nitrogen O2 – Oxygen H2O – Water vapor Ar – Argon CO2 – Carbon dioxide Trace gases Ne...

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Oxygen While nitrogen, as the main gas in our atmosphere at more than 78 Vol.-%, is completely inert and, despite its excess, cannot be used by plants as a much needed fertilizer in this gaseous state, oxygen is very reactive and forms the basis of our breathing and existence, moreover: the basis of nearly every living being. There is nearly 21 Vol.-% oxygen in our atmosphere. Oxygen deficiency is life-threatening and cannot be detected by our sense of smell. As a general rule, oxygen deficiency is caused by the release of inert gases, which then in turn displace oxygen. Since roughly one-fifth...

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Gases and vapors are almost always dangerous! If gases do not exist in their familiar and breathable atmospheric compositions, safe breathing is already at risk. Furthermore: All gases are potentially dangerous. Whether in liquefied, compressed or normal state – it is their concentration that is crucial. There are basically three categories of risk: – Risk of explosion (Ex) by flammable gases – Oxygen (Ox) Risk of asphyxiation due to oxygen displacement Risk of increased flammability due to oxygen enrichment – Risk of poisoning (Tox) by toxic gases Without auxiliary tools, humans are not able...

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Toxic Gases and Vapors The toxicity of gases and vapors used in industrial processes is determined using laboratory experiments that calculate the LC50 rate. Based on these investigations and additional scientific and occupational health investigations, authorized commissions in several countries make their recommendations for limit values, which are then legally binding. In Germany, this is the Federal Institue for Occupational Safety and Health (BauA). These limit values are defined to prevent employees from being harmed, provided they do not breathe in a higher gas concentration than the stated...

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Flammable Gases and Vapors Flammable gases become more dangerous when they have a relatively low explosion limit (LEL). Flammable vapors become more dangerous when they have a relatively low flash point. The flash point is defined by the liquid's temperature-dependent Vapor LEL LEL Flash Vapor Ignition Vol.-% g/nf Point Pressure Temperature Ethylene oxide Methyl chloride Only flammable flash point flash points Flammable Gases and Vapors

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LEL and Preventive Explosion Protection Flammable gases and vapors can form flammable mixtures when combined with air, but only if the proportion of flammable gas and oxygen (or air) is within certain limits. The lower explosion limit (LEL) is a combustion gas-air mixture which under standard conditions, can be ignited and will continue to burn gases and vapors is in the range of mixtures is 4 Vol.-%, and thus a test Concentration limitation This behavior is very important for practical explosion protection: If a flammable gas cannot be ignited . Carbon Monoxide . Methyl Bromide Methylene Chloride Acetyl...

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Flash Point of Flammable Liquids Although we speak of flammable liquids, it is not the liquid, but the vapor that is flammable. Only vapor can form a flammable mixture with atmospheric oxygen. Both the volatility of the vapor and its lower explosion limit (LEL) are measures for the risk of explosion. These are described by the flash point. To even be ignitable, the concentration of the liquid’s vapor above the liquid’s surface must exceed the LEL. The amount of vapor generated determines whether or not it ignites. The vapor pressure, which is dependent on the liquid’s temperature, is responsible...

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Concentrations And Their Calculation Concentrations are specified as the percentage of a substance in a reference substance. In regards to the measurement of hazardous substances in the air, a concentration is used to define the quantity of the substance in reference to air. A corresponding dimension is used in order to gain simple, manageable figures for the specification of a concentration. High concentrations are generally specified in percent by volume (Vol.-%). This corresponds to a defined amount of the substance in 100 parts air, for example air consists of 21 Vol.-% oxygen (100 parts air...

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Today, gas detector tubes are one of the classic measurement methods for gas analysis. This versatile system can be used within numerous applications in industrial fields, the fire service and hazardous material control in laboratories, for environmental research and many other areas. Dräger-Tubes can be schematically classified utilizing the following criteria: Gas measurement with Dräger-Tubes Short-term tubes Suction characteristic of Dräger accuro® Dräger accuro® The Dräger-Tube measurement system consists of a Dräger-Tube and a Dräger pump. Each DrägerTube contains a very sensitive reagent...

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All Dräger Safety catalogs and technical brochures

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