Fire Damage Chloride Testing
During a fire it is not uncommon for the levels of Chloride to increase. This is often due to the combustion of PVC (Poly Vinyl Chloride) which, as well as being present in the form of plastic objects and disposables, is also the material used to insulate electrical wires and cables.
The combustion of PVC will cause it to break down into its individual components. The Carbon is released in the form of Carbon Dioxide however the bound Chloride is released into its ionic form and will combine with Hydrogen to produce Hydrochloric acid (HCl). During the active fire the HCl will be in the vapour phase and will combine with any water vapour and disperse readily. When the fire is extinguished the HCl will settle and concentrate on any exposed surface.
When the Acid falls onto metal components and surfaces the risk of corrosion is very real. At elevated concentrations corrosion can occur rapidly particularly if the metal has retained some of the latent heat. Mild steel is most at danger where the HCl will convert Iron (II) to Iron(III) commonly known as rust!!
Any water ingress from extinguishers or weather or other control systems will dilute the HCl but will also enable the spread of the acid.
The Chloride Test Kit from EDT directION will enable the assessor to measure the level of Chloride over a defined area and display this result in Parts per million) ppm Chloride. The unit normally used in the industry is µg.cm⁻². To convert this reading just multiply the result by 0.8.
e.g. Result is 10ppm Chloride x 0.8 = 8 µg.cm⁻²
The normal background or natural level of Chloride contamination is between 1-5 µg.cm⁻². This will however depend if the premises are close to the sea or near a heavily salted road.
Quickly identifying the risk of corrosion to metal components or structures is essential to prevent further damage and quickly identify potential further risks.
It is advised to take several measurements to get a representative profile. The flexible template is 5cm x 5cm. Given that there is a natural background of Chloride contamination it is advisable to take a “Blank” swab and subtract this from the result.
The QPFire-Kit provides everything needed to carry out Chloride testing after a fire. The result is given directly in ppm Chloride which is multiplied by a factor to provide a Chloride µg/cm² result.
Visit our YouTube Channel for more content and methods.