ISO DIS 20435-1

Description / Abstract: This International Standard specifies general requirements for construction, testing and performance, and describes the test methods that apply to portable, transportable, and fixed equipment for the detection and measurement of toxic gases and vapours in workplace atmospheres and other industrial and commercial applications.

This International Standard is applicable to continuously sensing equipment whose primary purpose is to provide an indication, alarm and/or other output function the purpose of which is to indicate the presence of a toxic gas or vapour in the atmosphere and in some cases to initiate automatic or manual protective action(s). It is applicable to equipment in which the sensor generates an electrical signal when gas is present.

This standard applies to two types of equipment:

• 
  
  Type HM (Health Monitoring) ‘occupational exposure’ equipment:

For occupational exposure measurement, the performance requirements are focused on uncertainty of measurement of gas concentrations in the region of Occupational Exposure Limit Values (OELV). The upper limit of measurement will be defined by the manufacturer in accordance with 4.2.1.

• 
  
  Type SM (Safety Monitoring) ‘general gas detection’ equipment:

For general gas detection applications (e.g. safety warning, leak detection), the performance requirements are focused on alarm signalling. The upper limit of measurement will be defined by the manufacturer.

In general, the requirements for accuracy will be higher for Type HM equipment than for Type SM equipment. The same equipment may meet the requirements of both Type HM and Type SM.

For equipment used for sensing the presence of multiple gases this standard applies only to the detection of toxic gas or vapour.

This International Standard is not applicable to equipment:

– with samplers and concentrators such as sorbents or paper tape having an irreversible indication;

– used for the measurement of gases and vapours related to the risk of explosion;

– used for the measurement of oxygen;

– used only in laboratories for analysis or measurem ent;

– used only for process measurement purposes;

– used in the domestic environment;

– used in environmental air pollution monitoring;

– used for open-path (line of sight) area gas measurement;

– used for ventilation control in car parks or tunnels.