I'm very sorry to hear about your fire Jools.
I've been in the business of Fire and flood restoration since 1993 and I was an Insurance Adjuster for 15 years before then so I've restored hundreds and hundreds of fire damaged buildings over the years from small losses to very large apartment building fires costing several million dollars to restore. So, I hope that I can give you a few pointers that will help you navigate through the process of proper and effective remediation.
My apologies for the length of my post but it is a vast subject and my response is actually short and won't address all of the issues that a good fire restorer will.
Firstly, you MUST locate a good restoration contractor. That is, a contractor that specializes in fire restoration and that contractor is certified to do the work. Here in Canada and the U.S. The restoration industry certification is called IICRC (Google this) and there different levels of certification with one especially for Fire. Also, some IICRC individuals will seek their CR or certified restorer designation. I'm sure that in the UK you will have similar certication standards for this kind of work.
Resist the temptation to use a non-fire specialist contracting firm to complete the repairs just because they may be cheaper. You will only be likely unhappy with the result and any problems may not manifest themselves for a year or more!
With a kitchen fire (dishwasher is the source in this case) you must understand that a fire is simply a chemical reaction and the plastics burned are carbonized and distributed through the air due to heat transfer. Hot air from a fire tends to move towards colder air zones and this hot smoke "pressure" will forcibly move into small voids such as the gaps that exist between the backs of cabinets where they meet the walls and even will penetrate into wall electrical outlets harbouring the smoke contaminates. Also, the smoke particles are "charged" due to the fire chemical reaction and these charged particles tend to concentrate onto metal items. In heavy soot fires you will even notice that soot will concentrate on the wall where the drywall nails/screw fasteners are located as it acts kind of like a magnet. Also, when we get notice of a fire our first attack is cleaning the metal sinks and taps as well as other expensive metal surfaces as the smoke is heaviest here and because petroleum with sulfur is used in plastic production the result of burning plastic creates smoke particles that will etch metal in a few days in a heavy soot fire as the sulfur binds with moisture in the air essentially creating a form of sulfuric acid!!!
If improper restoration techniques are employed, any hidden smoke particulate will continue to off gas for years and I've seen jobs done by regular contractors that missed areas or voids and the homeowners noting that in the summertime when the weather is really hot they could smell lingering smoke smell. Heat re-activates the off gassing effect on surfaces and the cumulative untreated surfaces all contribute to the effect and later can be difficult to attack so it's best to make sure that all voids are treated properly from the start. I've chased smoke through pipes chases in apartment buildings several stories higher than the source into only to find wall voids three stories distant filled with smoke because of the smoke pressure involved!
While this is no means a replacement for engaging an experienced fire restorer I'll list some other processes and methods to address areas of concern.
1. Ozone. Is generally a pretty good tool in the arsenal against smoke smell but it is NOT the panacea. Think of when you go camping and your sleeping bag may smell of smoke but if you hang it up for a few days the smell deminishes with time, that is normal off gassing of the smoke particles and natural ozone plays a small factor. Ozone generators saturate the fire zone and because it is a gas it will treat areas that you can't get into to clean or seal. It is used in conjunction with proper cleaning, deodorizations and sealing techniques.
Simplified, the ozone generator uses the corona effect (electrical arc between two metal plates with a fan passing air past it) to alter the O2 molecules in the ambient air splitting the O2 molecules into single oxygen molecules and these single O molecules attach themselves to other O2 molecules and it becomes O3 which is Ozone. This ozone gas has a fairly short half life and will revert back to O2 on its own but some units we've owned also have a cycle to destroy the O3 quicker when done.
There are quite a few cautions associated with ozone though, in heavy concentrations it will affect rubber based products. As an experiement, in our ozone chamber at the shop we placed in the room a bag of New elastic rubber bands to be processed with other goods for a 12 hour cycle. Afterwards the rubber bands when stretched broke into hundreds of small pieces as if they were 10 years old. Any and all rubber and some plastics need to be coated with Vaseline to protect the rubber. Plus, plants don't do well and people cannot be present while the machines are doing their thing.
Also ozone may not always be effective over time, it was as good as it gets 10 years ago but now there are new alternatives that take the decontamination efficacy to a higher level and that is photo catalytic oxidation or PCO and I've seen it do amazing things that ozone can't address. The info on this product is as listed below so I'll let the quote below explain the process.
"The BIOSWEEP™ process employs proven technology called photocatalytic oxidation (PCO) in a five-stage process to produce simultaneous, interrelated forms of oxidation to eradicate airborne organic contaminants. These vapour compounds are unsurpassed in field applications for their penetrating oxidative power to remove virtually any embedded or persistent odour.Biosweep Multiphase Process
1. Germicidal UV Radiation
Air comes into the bottom rear of the BIOSWEEP™ unit. High intensity germicidal irradiation is lethal to incoming airborne microorganisms, creating peptide bonds within their DNA, preventing them from further replication. All other slices of the UV Band are used as well. break 2. Powerful Singlet Oxygen and Oxyradical Plasma
A dense cloud of powerful molecular oxidizers attack bio-particles and rapidly begin breaking the carbon bonds that form their cellular matter. Approximately 70% of the systems energy goes into creating this powerful sterilizing plasma gas, which includes singlet oxygen, superoxide, hydrogen peroxide and three oxyradicals: hydroxyl radicals, the atomic oxygen radical, and hydro peroxide radicals. These agents remain in the chamber. break 3. Concentrated O3, H2 O2
Purified trivalent oxygen, called ozone, is produced which contributes to oxidization within the chamber and production of more oxyradicals. Bulk ozone and hydrogen peroxide molecules leave the top of the unit to continue their work outside the chamber for another 30-45 minutes before decaying harmlessly back to the natural elements from which they were made. break 4. Photocatalytic Production of Hydroxyl Radicals
Special nanoparticles coated on the entire inner chamber wall undergo a photocatalytic reaction driven by the UV energy field. They convert water vapour in the air or feed gas into more hydroxyl radicals projecting from the entire inner surface. The new oxyradicals break up passing organic matter and generate more oxyradicals from the O3 concentration present. break 5. HEPA Filtration, Optional Supplemental Feed Gas"
2. Smoke or soot damaged surfaces like drywall needs to be properly cleaned and prepared prior to sealing and painting. The loose soot is removed using what is called here as a "chem" sponge which is a misnomer as there is no chemicals involved. Essentially, it is a large soft rubber eraser that "drags" the loose soot off the wall. Don't try to clean the walls with a wet cleaning cloth as it will just smear the soot on the wall.
Then, the drywall is soot sealed with products like KILZ or BINS and must be the oil or shellac based type as you are sealing in the remaining soot discolouration and prevent off gassing of the smoke particles. Latex based products won't seal or create the barrier required to prevent the smoke particles from off gassing further. Then, the final paint top coats can be applied as normal.
I know that your fire isn't as severe but in heavy fires with some minor surface charring to wood framing members (not structurally damaged and not readily or easily removed) or for mould claims in attics where the underside or the roof sheathing has surface mould we use dry ice blasting or sometime walnut, corn or soda blasting to abrade the contaminated surfaces without causing damages. Dry ice blasting is great as it sublimates or turns from a solid to a gas directly without becoming a liquid so the soot just falls off and is vacuumed up off the floor. We did a 100,000 sf industrial warehouse using this method to clean all the nooks and crannies of the steel web trusses 24 feet high and traditional hand cleaning methods would've been slow, less effective compared to blasting it.
In short, don't just hire any old contractor, as the risk is too high for that type of contractor to miss important steps or not understand the specific requirements for effective and thorough remediation. Use a specialist!!!
