There are principally three types of instrument for testing the atmosphere in an enclosed space:

1.      The Combustible Gas Indictor;

2.      The Chemical Absorption Type of Detector;

3.      The Oxygen Meter.

         目前基本上有三种仪器可以帮助我们测试封闭场所内的气体成分，它们有：

1.      可燃气体指示器；

2.      化学气体探测器；

3.      氧气分析仪。

（1）The combustible gas indicator (or explosimter) detects the presence and proportion

          of hydrocarbon vapour in air, if is not suitable for detecting gases and vapours at

          very low O₂ content. It dose not indicate oxygen deficiency or reliably indicate the

          presence of hydrogen, nor dose it measure toxicity in the atmosphere.

（一）可燃气体指示器（EXPLOSIMETER）：

            用于探测空气中氢化碳气体成分和其所占比例，但此仪器不适用于缺氧环境

   （可使用TANK  SCOPE），也不能显示氧气不足或可靠指出氧气的存在，以及

    空气中存有其它有毒气体。

（2）Chemical absorption detectors are particularly useful for detecting the presence of  

          specific gases and vapours at THRESHOLD LIMIT VALUE (TLV) levels.

          Threshold Limit Values (usually quoted for gases in parts per million – ppm) relate

          to daily exposure rates of 8 hours but these values of average tolerable

          concentration are a useful guide in the control of hazards in confined spaces.

（二）化学探测器

            用此仪器测试一些特殊气体以确定中毒临界值（TLV—又称安全极限值，是

    指有毒气体在空气中对人员安全的最高浓度限制值，以其体积含量在空气中的百

    万分比PPM表示。人员在其中毒临界值以下环境中每天8小时工作，长时期也不

    会危害健康），探测到的是有毒气体的平均浓度值，用于控制在封闭场所内可能

    发生的中毒危险。

（3）Oxygen testing equipment should be carried on all ships and should be used to

          measure the percentage of oxygen present within the space where it is suspected

          that there may be a deficiency.

（三）氧气分析仪

            所有船舶都应携带氧气分析仪，以便测量空气中氧气含量，尤其是一些受怀

    疑的场所中氧气含量是否足够。

PRICIPLE  操作原理

(1)    COMBUSTIBLE  GAS

Catalytic combustion method is applied. If an air contained combustible gas comes

in contact with detective element which is heated up at a proper temperature, the combustible gas will produce a heat by a chemical reaction with oxygen in air and  catalyst on the element. The heat of combustion is proportional to gas concentration at the range of less than “LEL” (Lower Explosive Limit). As the electric resistance of the element is changed owing to rise of temperature by the heat reaction, the electrical output is proportion to the gas concentration can be obtained.

可燃气体:

         利用电催化原理。当可燃气体接触因通电而发热的探测头时，可燃气体被

引燃，燃烧所产生的温度与可燃气体在可燃下限的浓度成正比，探测头内铂丝线圈电阻随温度升高而加大，通过桥式电路，电阻的变化转化成电位差，从仪表显示出来。

(2)    CHEMICAL VAPOURS / GASES

Coloriometric gas detector tube method is applied. When chemical vapours or gases in contact with a specific reagent, the reagent will stain from the original color by means of a chemical reaction and existence of the gas is known.

化学气体：

              利用试剂变色原理。当化学气体通过内藏试剂的玻璃管时，试剂因与气体

      接触产生化学反应而变色，从而就知道了有毒气体的存在。

(3)    OXYGEN

Galvanic cell method is applied. The oxygen permeating through a “FEP” ( A copolymer or ethylene hexafluoride and polypropylene ) shall act to the cell composed of a golden cathode, a lead anode and an electrolyte and a current in proportion to the oxygen concentration shall take place. The oxygen concentration is determined by amplifying the output of the cell.

氧气：

              使用电化学电池方法。当氧分子渗透过一些聚合物（由次乙基六氟与多丙

      稀组成），在流向由一金质阴极、一铅阳极及电解液组成的电化学电池时，在

      阴极产生化学反应，并使电池产生电动势（电流），电流的大小与阴极 / 电解

      质结合的氧气成正比。

PLEASE  NOTE:

Before using any test instrument, the manufacturer’s instruction and advice on the limitations of the equipment should always be consulted and understood.

请注意：