This article will focus specifically on the removal of smoke and soot after a fire. Apart from the hazards to human health and damage to property soot causes, research published in the Journal of Geophysical Research suggests that soot is the second-largest cause of global warming.
What is Soot?
Soot is the product of incomplete combustion, i.e. burning within a limited supply of oxygen. Soot is an extremely fine, black powdery substance usually made of amorphous (without defined shape) carbon. A product of the gas phase of combustion it forms particle agglomerates which coat and permeate surfaces. Its composition is determined by the reactants that entered the combustion reaction. Depending on the substances that have been burned, soot will contain chemicals, metals, soils, dust and acids.
Particles of soot are extremely small, often around 0.25 µm (millionths of a metre), much smaller than the dust seen ‘floating’ in the air. To put this into perspective, the diameter of a human hair is around 100 µm, or 0.00394 inches. The combination of its toxicity and its size make soot particularly hazardous to human health. Soot is created during a fire and is produced either as a particulate (solid) or a gas which will become a solid after release. Given the small size and light weight, soot can travel far from its source.
This magnified image of agglomerated soot is from an industrial fire in a plumbing warehouse. To illustrate how far soot will travel, this particular piece was collected from a home a few hundred metres away.
What is smoke?
Smoke is emitted when a substance undergoes combustion. It is a visible, airborne suspension of mainly carbon particles. As with soot, the components of smoke will be determined by the substances that were burned. Apart from carbon, tar, oils and ash, smoke will often contain thousands of chemicals; smoke is an irritant and can be highly toxic.
The hazards of soot and smoke
A fire in any structure will probably involve the combustion of: plastics, fabrics, wood, carpets, foams and asbestos among other materials. A fire in an older building will produce residues containing asbestos, lead oxides, arsenic among others whereas a fire in a newer structure will produce hazards including isocyanates and dioxins. When dealing with soot and smoke damage, ensure you are aware of the hazards you are dealing with and how to avoid them.
Pipes & fittings, cables and so many other construction materials are made from Polyvinylchloride (PVC), it is the most commonly used plastic globally. When PVC is burned, chlorine atoms are released which inhibit combustion. The chlorine atoms bind to hydrogen atoms to form hydrogen chloride, a sensory and pulmonary irritant.
The particle size of soot and smoke is part of the problem, it enables these toxic and damaging particles to enter every space and permeate materials where they continue to be hazardous. When these airborne particles are under the high pressure of a fire, they are driven deeper into the fabric of a building and its contents where they remain, unless completely removed.
Inhalation of smoke is the primary cause of death in fires that occur indoors. 75% of fire victims die as a result of the effects of smoke.
- Smoke can contain poisonous gases such as hydrogen chloride and carbon monoxide
- Smoke is an asphyxiant, an irritant and can be highly toxic
- Smoke obscures visibility causing disorientation
- Smoke contains compounds which are flammable; potentially self-igniting if enough oxygen is present or re-igniting when in contact with flames
- Smoke damages buildings, often more so than the fire itself
- Smoke will stain and leave a powerful odour that is very difficult to remove
Soot contamination is a serious issue that cannot be left; it needs to be dealt with correctly and immediately to minimise harm.
- Soot is a respiratory hazard, it enters the respiratory system during inhalation and can penetrate lung tissue as far down as the alveoli where gas exchange occurs
- Soot is acidic, corrosive and will damage the surfaces it contacts
- Soot has been linked to a significant increase in the number of deaths from lung cancer
- Soot is classified by the [EPA] as a ‘criteria pollutant’, an air pollutant
- Soot can contain highly toxic chemicals that will be hazardous to health and contaminate the environment
How to remove soot and smoke
Safety is the primary concern; if damage is caused by a significant fire seek the advice of a professional fire damage remediation company. It is potentially dangerous and a false economy to undertake the clean-up of fire damage without the correct equipment or a high level of competence. Secondary damage will continue to pose serious threats to property and health if the remediation process wasn’t thorough and complete. Different types of fire will cause different types of residue; each fire requires a specific and tailored approach.
For lighter residues and limited fire damage
- Do not enter any structure unless you have been told it is safe to do so by a professional.
- Ensure area is well ventilated.
- Wear appropriate Personal Protective Equipment (PPE) to protect lungs, eyes, skin and body including: gloves, goggles, footwear, respirator, chemical suit. Guidance can be found here.
- Remove any items that are unsalvageable and install dehumidifiers if water has been used as an extinguisher, excess moisture will cause the growth of mould.
- For carpet: an extraction machine or professional carpet cleaner, avoid impact as this will embed the soot into the material.
- For hard, porous materials (wood, wallpaper, plaster, paint, wallboard, MDF): Use a dry chemical sponge, avoid adding moisture which will cause the soot to become absorbed into the material.
- For hard surfaces that are less porous (tile, glass, treated wood, metal, appliances): A damp sponge or mop with appropriate detergent
- Fabrics: May require professional and specific cleaning. An upright vacuum may force soot deeper into the fabric. Using an appropriate vacuum with adequate filters to withhold soot particles, hold the nozzle a small distance away from the fabric to lift soot away from the fabric.
- Cover items as they are cleaned to prevent re-contamination.
- Invisible soot: Don’t forget to remove fixtures and fittings and clean all spaces, ducts and vents thoroughly, soot left will continue to present a hazard to health and to damage property.
For significant fire damage and heavier residues
This level of remediation work should only be undertaken with the appropriate level of expertise and correct equipment. Time and costs could escalate if the remediation process is not carried out effectively in the first instance. There are a variety of techniques that can be deployed, all dependent on the specific situation and materials involved. The hazards caused by fire require specific knowledge, techniques and equipment to ensure no risks remain.
- Chloride testing – The chloride residues left by a fire will cause irreparable damage to the structures they contaminate throughout the building. They are highly toxic and hazardous to health and if undetected, will continue to cause damage in the long term. The correct chloride detection method should be applied throughout the site to inform the cleaning process. This stage is vital to protect personnel and property.
- Wet and dry cleaning – Use for differing grades of carpets, upholstery and fabric. Dry cleaning methods should be carried out by professionals and utilise specific counteractants specific to the type of fire. Wet cleaning involves the application of detergent solutions to fire damaged textiles, may require soaking first; seek professional advice.
- Sodium bicarbonate blasting – for the removal of residue, corrosion, grease and oil from surfaces. This is an eco-friendly and bio-degradable method of removing residues without chemicals and with minimal damage to surfaces. Suitable for metal, timber and brick, internal and external surfaces that would be more challenging to clean.
- Air scrubbing – The acrid odour that lingers after a fire is caused by residues such as soot. Air can be filtered and sterilised if necessary to remove all hazardous particles including pathogens. This process should be undertaken by trained technicians.
- Ultrasonic cleaning – A cleaning system that uses energy in the form of high frequency signals to effectively remove deeply embedded soot and smoke particles. This process should also be carried out by qualified and experienced technicians.
- Sanitation and decontamination – All contaminated material must be removed and disposed of correctly or thoroughly cleaned using appropriate techniques. Complete decontamination should be followed by testing and certification.
All employers have a duty of care to prevent exposing personnel to any unnecessary risk. Soot and smoke will permeate every part of a building and it is vital that ‘no stone is left unturned’ to eliminate risk and ensure health and safety. The risks posed by fire damage are serious and should not be taken by any person who is unskilled or untrained to do so.
If in any doubt, always consult a trusted, experienced professional company
Ideal Response have a reputation for providing exceptional fire damage remediation work in London and the South East. We understand the need for fast action and aim to be on-site within two hours of your call. We will implement a start-to-finish solution from the initial assessment through to completion with the presentation of a hygiene guarantee certificate for your records and for your peace of mind.