With the acquisition of two new FTIR systems, one in France and one in UK, Efectis is now able to provide a wide range of gas analyses associated with fire tests.

Using Fourier Transform Infrared Spectroscopy, fire effluent is filtered and then continuously irradiated by two beams of IR light which pass through the sample via different paths. When the beams subsequently combine, the resulting ‘interferogram’ can be resolved mathematically (Fourier Transform) to determine the infrared absorption as a function of frequency and can be used to identify and quantify different species. The value of FTIR over classical infrared spectroscopy is that samples can be analysed for many components in one sample and a complete spectrum can be obtained over a relatively short time period (a few seconds). Software can identify and quantify many infrared active species from a single sample scan. These result in the possibility of quasi-continuous concentration/time plots when the FTIR is connected directly to the sampling line. Sensitivity is dependent on the optical path length through the analysed gas that passes through the gas cell, and on the type of detector.

Fire effluent gas and vapour analysis using FTIR is now routinely used in the field of fire safety, often following the original guidance from a European Union funded research programme ‘Smoke Analysis by FTIR spectrometry’ (SAFIR) and then using ISO 19702 standard.

Gases commonly analysed with this method include CO, CO2, hydrogen halides (HCl, HBr, HF), sulphur-containing species (H2S, SO2), nitric oxides (NO, NO2, N2O) and aldehydes. Other species such as light hydrocarbons are also easily measured (CH4, C2H2, C2H4 for example). These analyses can be completed with semi-quantitative or qualitative analysis of a wide range of gases on demand. The FTIR technique is capable of measuring concentrations below 10 ppm and allows dynamic on-line measurement of these concentrations, typically every five seconds.

In summary, this technique involves sampling gas through a single measurement cell and recording the spectral response. The absorbing frequencies and the intensity of absorption at those frequencies allow identification and quantification (through suitable calibration) respectively.

Applications are wider nowadays:

These data are particularly valuable for use in mathematical models that calculate toxicity of fire effluents as a function of time, or simply to understand more fire chemistry.

Contact: Eric Guillaume – eric.guillaume@efectis.com