Selection Guide for Toxic‑Hazardous Gas Detectors
Against the backdrop of deteriorating living environment and severe environmental‑protection situation, stricter pollution‑control measures have been implemented. Workplaces and manufacturing facilities involving toxic‑hazardous gases are strengthening internal management. Gas concentration detectors and gas monitoring alarms become essential equipment. Gas detectors are instruments for detecting gas‑leakage concentration, including portable, handheld, fixed‑type and on‑line gas detectors.
Modern toxic‑hazardous gas detectors adopt advanced imported electrochemical sensors from Germany or the United States. They operate on the well‑established controlled‑potential electrolysis principle. Three electrodes are installed inside the electrolytic cell: working electrode, counter electrode and reference electrode, with a certain polarization voltage applied. Different toxic‑hazardous gases can be measured by replacing sensors and adjusting polarization voltage. Target gas passes through the membrane to the working electrode and triggers redox reaction. The sensor outputs a tiny current proportional to gas concentration. The current signal is sampled and converted into voltage, amplified and transformed, then gas concentration readings in ppm within measuring range are output as 4‑20 mA standard signal.
Structure and working principle of combustible‑gas detectors New‑generation low‑power high‑anti‑interference carrier catalytic elements are adopted, forming a measuring bridge circuit together with two fixed resistors. When combustible gas diffuses onto the sensing element surface, catalytic reaction occurs. Output voltage is proportional to combustible‑gas concentration. After amplification and voltage‑current conversion, readings within full scale below lower explosive limit (ppm or %LEL) are converted into 4‑20 mA standard output signal.
Principle of oxygen sensor for oxygen gas detectors Galvanic cell principle is applied. The galvanic cell contains lead anode and silver cathode, isolated from ambient atmosphere by a membrane. Oxygen penetrates the membrane and reaches the cathode. The signal is amplified and converted, and oxygen concentration within 0‑30 %VOL is output as 4‑20 mA standard signal.
Above are the common working principles of mainstream gas detectors. Based on factory and site conditions, gas detectors are widely used in agriculture, chemical industry, construction, electric power, fire‑fighting, natural‑gas industry, general industry, toxic‑material handling, iron‑steel industry, petrochemical industry, sewage treatment, pharmaceutical industry, food industry, water‑treatment industry and tobacco industry.
Application scope keeps expanding. In pharmaceutical industry, gas detectors monitor various volatile organic compounds. Many raw materials and intermediates are toxic or flammable‑explosive substances. Similar to chemical plants, pharmaceutical sites require monitoring for leakage of toxic, hazardous or combustible‑explosive gases.
In food‑processing industry, gases such as ClO₂, CO₂ and O₂ are used for sterilization and fresh‑keeping. Corresponding fixed gas detectors are deployed on‑site for process control and leakage monitoring. Besides, gas detectors are also widely used in pesticide industry, semiconductor manufacturing and customs inspection.
