Liquids with a high flash point and a Class C hazard also have an explosive limit.
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I have come across liquids with a high flash point and a Category C level of hazard, for which the explosion limit can also be found. Therefore: 1. It was found that the liquid has a high flash point and belongs to Category C in terms of hazard level; however, its explosive limit could not be determined. This does not mean that the substance cannot create an explosive gas environment. But according to the specifications, combustible gas detection and alarm devices are only required for substances in Categories A and B A, that is, those with a flash point below 45°C.
I’m also puzzled; class C flammable liquids may also be classified as class B A depending on the operating temperature, and this factor needs to be taken into account in practice.
1. The alarm settings are based on the design specifications for flammable and toxic gases as outlined in petrochemical industry standards; they apply to areas classified as Category A and B, as well as those that are toxic. Given such risks, we install detection and alarm systems in these Category A, B, and toxic areas； 2. The explosion limit is merely a physical property of a pure medium under certain standards; therefore, when conducting tests related to special operations in devices or locations, the lower limit for measuring concentrations should be determined as a percentage of the lower limit of the minimum explosive concentration. This is directly related to our controls for special operations ； 3. Current combustible gas detection instruments are calibrated using methane or butane gas, and they employ catalytic combustion or other oxidation techniques. As a result, whether the combustible substance is in gas form or as vapor, it can be detected by the sensor through catalytic combustion or other oxidation processes, and a response can be generated – the type of substance doesn’t really matter. If there is any difference, it’s probably that the measurement accuracy will be lower compared to those designed for specific gases such as methane, H2S, or hydrogen. On the other hand, we certainly prioritize detecting substances with high sensitivity, high danger potential, and low explosion limits, and sensors are designed accordingly. So... there’s no need for concern. If Class C substances can produce volatile gases (depending on operating conditions), then operational controls are still necessary; in such cases, the concentration to be monitored is determined according to criterion 2.