Smoke parameter

Smoke has usually been measured in the NBS smoke chamber. Such results cannot be correlated with full scale fire results and do not predict fire hazard. Rate of heat release (RHR) calorimeters (e.g. NBS Cone (Cone) and Ohio State University (OSU)) can be used to determine the best properties associated with fire hazard, as well as smoke. Results from the Cone RHR correlate with full-scale fire results. The best way to determine the fire hazard associated with smoke, for materials which do not burn up completely in a fire, is by using RHR to measure combined smoke and heat release variables, such as smoke parameter or smoke factor. 

This work measured smoke and heat released from burning 17 materials, in the Cone and OSU and smoke in the NBS smoke chamber. Results from the RHR calorimeters correlate well with each other while those from the smoke chamber do not. This suggests that the smoke parameter and smoke factor, from either RHR calorimeter, are excellent measures of smoke hazard. 

The Cone calorimeter yields smoke results which have been shown to correlate with those from full scale fires [10, 15-18]. The concept of a combined heat and smoke release measurement variable for small scale tests has been put into mathematical terms for the cone calorimeter smoke parameter (SmkPar) [10]. It is the product of the maximum rate of heat release and the average specific extinction area (a measure of smoke obscuration). The correlation between this smoke parameter and the smoke obscuration in full scale tests has been found to be excellent [10]. The corresponding equation is ... 

This parameter, the smoke parameter, is based on continuous mass loss measurements, since the specific extinction area is a function of the mass loss rate. A normal OSU calorimeter cannot, thus, be used to measure smoke parameter. An alternative approach is to determine similar properties, based on the same concept, but using variables which can be measured in isolation from the sample mass. The product of the specific extinction area by the mass loss rate per unit area is the rate of smoke release. A smoke factor (SmkFct) can thus be defined as the product of the total smoke released (time integral of the rate of smoke release) by the maximum rate of heat release [19], In order to test the validity of this magnitude, it is important to verify its correlation with the smoke parameter measured in the Cone calorimeter. 

It has already been shown that the Cone calorimeter smoke parameter correlates well with the obscuration in full-scale fires (Equation 1). At least four other correlations have also been found for Cone data (a) peak specific extinction area results parallel those of furniture calorimeter work [12] (b) specific extinction area of simple fuels burnt in the cone calorimeter correlates well with the value at a much larger scale, at similar fuel burning rates [15] (c)maximum rate of heat release values predicted from Cone data tie in well with corresponding full scale room furniture fire results [16] and (d) a function based on total heat release and time to ignition accurately predicts the relative rankings of wall lining materials in terms of times to flashover in a full room [22]. 

For the specific extinction area correlation described in (a) those materials which did not burn completely in the full-scale were specifically excluded [12]. The small scale test always leads to complete consumption of the sample. Therefore, more smoke is being produced in the small scale test than in real fires for those materials usually associated with lower fire hazards. This is exactly the kind of issue that is being remedied by measurements of smoke parameter or smoke factor. 

Tables VII-IX present heat release data for the same materials as in Tables IV-VI. The Tables also present the same smoke data as measured with the OSU calorimeter, plus smoke parameter information (SmkPar in MW/kg).

Linear correlations were thus attempted for peak rate of heat release, total heat released after 15 min. and smoke factor between both calorimeters. Furthermore, linear correlations were also attempted between OSU calorimeter smoke factors and Cone calorimeter smoke parameters and between Cone calorimeter smoke factors and Cone calorimeter smoke parameters. Figures 1-3 show some of the results. 

Figure 2. Correlation between the OSU smoke factor and the cone smoke parameter at an incident heat flux of 40 kW/m2.

A summary of the results of correlation models for smoke factor and smoke parameter is shown in Table X. For comparison purposes, correlation models for OSU and Cone calorimeter peak rates of heat release are also shown in Table X, together with one of the total heat release models. 

Smoke parameter (in the Cone calorimeter) and smoke factor (in both calorimeters) are combined properties of smoke obscuration and heat release which compensate for the incomplete burning of fire retardant samples and which should predict smoke hazard in real fires. 

Note FPI, fire performance index (m2 s/kW) RHR, rate of heat release (kW/m2) SEA, smoke extinction area (m2/kg) SP, smoke parameter (MW/kg) TTI, time to ignition (s). 

An investigation was carried out into the fire retardant behaviour of zinc hydroxystannate-coated fillers (alumina trihydrate and magnesium hydroxide) in PVC and EVA cable formulations. Measurements were made of the limiting oxygen index, peak rate of heat release and smoke parameter and the data for unfilled and filled formulations compared. X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier-transform spectroscopy were used to study the filler-coating interaction. 16 refs. 

Smoke parameter The product of the average specific extinction area and the peak rate of heat release. This parameter indicates the amount of smoke generated MW/kg... 

Sample LOI Cone Peak rate of heat release (kWIm ) Cone Smoke parameter (MWIkg) ... 

---