Flare radiation monitor / heat flux sensor

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HF02 is a sensor that measures radiant heat flux or thermal radiation in the outdoor environment. A common application is monitoring the radiation emitted by flares. HF02 is certified for use in potentially explosive atmospheres, and is rated for radiation levels up to 15 x 103 W/m2. We recommend use of HF02 in a decision-supporting role only, and not to use measurements of HF02 as the main or sole source of information for judging safety.


HF02 is used in alarm systems, using the heat flux measurement to issue a warning in case of high thermal radiation exposure of equipment or personnel. It is typically installed close to a flare. A common assumption is that the heat flux level in a safe environment for personnel must not exceed 5 x 103 W/m2 (or 1.5 x 103 BTU/(hr∙ft2)). Above that heat flux level, or when the temperature of the sensor body exceeds 70 °C, an alarm is activated. A typical alarm system will include multiple HF01 sensors, all aimed at the main source of radiation, as well as other decision-supporting devices such as camera systems and temperature sensors. The sensor in HF02 measures the heat flux to its black (absorbing) surface, in the plane of the sensor, from a source in the field of view angle. It offers a measurement of the effective exposure for personnel and equipment from a source in the direction it is aimed at the location of the sensor. As the detector is essentially open (it has no protective windows) the measurement is influenced by wind in the same way as any exposed surface such as clothing worn by  personnel or the surface of equipment; increased wind speed leads to a reduction of the measured heat flux. Rain on the detector can also lead to cooling and a reduction of the measured heat flux.

To perform a heat flux measurement representative of human exposure or equipment exposure, the sensor temperature should be as close as possible to the ambient air temperature. This is the purpose of the sun / rain- and radiation screens of HF02 (in combination with cooling fins). They reduce radiative heating of the sensor by the sun. The screens also reduce the effect of wind and rain, reducing the risk of a false indication of a safe situation. HF02 is rated for use in potentially explosive environments. It is supplied with a product certificate specifying the ATEX rating as II 2 G EEx d IIC T6.

Using HF02 is easy. It can be connected directly to commonly used data logging systems. The heat flux in W/m2 is calculated by dividing the HF02 output, a small voltage, by the sensitivity. The sensitivity is provided with HF02 on its product certificate.


  • robust
  • all-weather
  • suitable for potentially explosive environments

Suggested use

  • outdoor flare monitoring  


  • longer cable: standard length of the high temperature metal sheathed cable as well as the low temperature extension cable is 3 m. Both can be extended up to 100 m.
  • sensitivity: we offer dedicated converters for HF02 to provide a standardised output
  • shielding options: the standard version has the sensor body and the high temperature cable connected to the shield/drain wire of the low temperature plastic cable. A shield disconnected from the high temperature metal cable and sensor body is offered as an option.


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