Buy smoke density test 61034 is all about the assessment of plastic used on a cable. This test is also integrated with the new CPR regulation in Europe for cables in EN 50399 and EN 50750.
In the case of fire, the smoke has many effects, one of the worst being visibility reduction.
It delays escaping from buildings, as the smoke is quickly felt like an impenetrable barrier
affecting breathing and irritating the eyes. Visibility (m) is assessed through smoke
opacity, by calculating its optical density, extinction coefficient or transmittance.
Finally, the effect of opacity on people is determined using models that take into
account the object they want to see through the smoke.
Transmittance is the ratio of transmitted light intensity through the smoke to incident light
intensity under specified conditions. It is dimensionless and is usually expressed as a
percentage. Without any smoke its value is 100%, decreasing with the smoke release.
I0: light intensity measured in the absence of smoke/transmittance = 100%
I: light intensity measured with smoke
3.2 Optical density
The Beer-Lambert law defines light absorption of a material, depending on its
properties. It can be used to determine the attenuation of light through the smoke for
a given path length. The optical density is usually obtained by measuring the
attenuation of a light beam passing through the smoke, using the Lambert-Beer law.
One of the main testing methods in the cable industry to assess the smoke
production potential in the case of a fire is described in the IEC/EN61034-1 and -2
standards. Cables are placed above a tank containing a specific fire source, mainly
ethanol, in a 27 m3cabin.
When the cable materials burn, smoke is released,
reducing the light intensity in the test chamber. This attenuation is measured by a
photocell placed in front of a white light beam at a fixed distance: path length of 3 m.
The final result is given in terms of transmittance, (%). Without any other
specification, the normal pass/fail criterion is 60% of light transmittance.
The equipment consists of:-
- 3-meter cube double-walled 2 mm thick steel chamber
- Mixing Fan
- Exhaust system
- Flame panels
- Ethanol tray
- Sample holder
- The light source of 3500-3000K
- White light detecting diode equivalent to the human eye
- Computer with copyright software for control and reporting of entire setup