1. Fixed gas detector
This is the most commonly used monitor in industrial production processes. It can be installed at specific leakage points to detect gas concentration. The fixed detector is generally two-type, the detection probe composed of a sensor and a transmitter is installed in the test site as one, and the secondary instrument composed of a circuit, a power supply and a display alarm device is installed in a safe place for easy monitoring. It should also be selected according to the type and concentration of the gas in the field, and pay attention to installing them in the part where the specific gas is most likely to leak, such as choosing the most effective height of the sensor installation according to the specific gravity of the gas.
2. Portable gas detector
Portable gas detector, it is easy to operate, small size, wear on the construction personnel, play a role in personal protection. Combustible gas detectors (LEL), photoionization detectors (PID) and compound gas detectors mostly use rechargeable batteries, so that they can generally work continuously for nearly 12 hours, so as such instruments are increasingly used in various factories and health departments.
According to the different sampling methods, the portable gas detector is divided into diffusion gas detector and pump gas detector. If it is an open occasion, such as an open work workshop to use this type of instrument as a safety alarm, you can use a portable diffused gas detector, because it can continuously, real-time and accurately display the concentration of toxic and harmful gases on the scene. This type of gas detector is also equipped with a vibration alarm device to avoid audible alarms in noisy environments, and it has a built-in computer chip to record peaks, STEL(15-minute short-term exposure level) and TWA(8-hour statistical weighted average) to provide specific guidance for worker health and safety. If you are entering a confined space, such as reaction tanks, storage tanks or containers, sewers or other underground pipelines, underground facilities, agricultural closed granaries, railway tank cars, ship cargo holds, tunnels and other workplaces, you must be tested before people enter, and you must be tested outside the confined space. At this point, Pump-suction type 4 gas detector confined space must be selected.
Because the gas distribution and gas types in different parts of the confined space (upper, middle and lower) are very different. For example: in the general sense, the proportion of combustible gases is relatively light, and most of them are distributed in the upper part of the confined space; The proportion of carbon monoxide and air is about the same, generally distributed in the middle of the confined space; Heavier gases, such as hydrogen sulfide, are found in the lower part of the confined space. At the same time, the oxygen concentration is also one of the kinds that must be tested. In addition, if considering the possible volatilization and leakage of organic materials in the tunnel, a detector that can detect organic gases is also needed. Therefore, when conducting gas detection in a confined space, the gas detector needs to have the following functions:
A. with built-in pumping function - so that it can be non-contact, partial detection.
B. with multi-gas detection function - to detect different spatial distribution of dangerous gases, including inorganic gases and organic gases.
C. with oxygen detection function - to prevent hypoxia or oxygen enrichment; Small size, does not affect the work of the portable instrument. Only in this way can guarantee staff safety before entering the confined space.
In addition, after entering the confined space, the gas composition should be continuously tested to avoid changes in the concentration of volatile organic compounds or other toxic and harmful gases caused by personnel entry, sudden leakage, temperature and other changes.