Fire Testing After a Structural Fire

Aug 14, 2018

If there is a fire in a kitchen, to what degree will the adjacent room be impacted by fire-related particles? What about a room on an entirely different floor? Testing for contaminants after a structural fire can be a key step in determining the scope of cleanup and restoration. Due to the length of time the claims process can take, some contaminants from a fire will dissipate before an inspector is called to assess. One contaminant that can persist is smoke residue. Often after a fire-damaged home has been restored, occupants will complain of residual smoke odor inside the home. These complaints often are due to residual smoke residue that may be hidden in the interstitial spaces of walls and ceilings.

For an inspector to create an informed sampling strategy they need to have details about the fire. A site visit can help them determine the possible extent of smoke and fire damage and create the best sampling plan. For example, was the fuel for the fire various building materials and furnishings? Or was the fuel-burning food as is the case with a protein-based fire? A structure fire can release huge amounts of smoke and particles throughout the home, where a protein fire usually does not produce much smoke and instead leaves behind a pungent-smelling residue.

There are many different ways to collect samples for smoke particles, and also different levels of laboratory analysis available. To add another layer of complexity, there is no clear consensus for sampling methodology (nor are there widely supported guidelines on data interpretation of fire-related particles). Beyond all this complexity, a big factor that an environmental professional has to deal with in a post-fire assessment is budget.

Picking the Right Spot

Depending on the type of fire and the surface you are testing, an inspector needs to make sure they are choosing the best type of sample for the situation. A “chem sponge” is a vulcanized rubber sponge that is used in many fire and smoke cleaning applications. These tools can be very useful in determining if a surface may have been affected by smoke and if it is a good area to collect a laboratory surface sample. When the chem sponge is pulled across a surface with potential smoke particles it will typically leave a dark black deposit on the sponge and would indicate an area from which to potentially collect a laboratory sample. Typical house dust will leave a white or gray deposit on the sponge.

Surface Samples

The two most common types of surface samples collected in a fire assessment are tape lifts and wipes. Tape lifts are done by using a clear adhesive tape that is pressed onto a surface. Particles deposited on the surface will adhere to the tape. Tape lift samples are a good option for samples that are going to be analyzed via optical microscopy. Tape lifts are a relatively inexpensive option to identify larger char fragments, which are the primary indicator of fire-related particles. Unfortunately, painted surfaces can often provide a false positive as the pigment can be mistaken for a fire-related particle. For that reason, the best surfaces for tape-lifts are unpainted metal, glass, plastic, and wood.

Wipe samples are also a good choice for surface sampling since they can be analyzed via most methods for both particles and chemical combustion by-products. Although more expensive than tape lifts, wipe samples can be used if the tape lift results are inconclusive regarding the presence of char.  Soot is considered a secondary indicator of fire-related particles. Due to its small size and instability, soot can only be collected on a wipe sample. With a wipe sample, more advanced analytical methods can be used, such as electron microscopy, or X-ray spectroscopy. Wipe samples that use alcohol should not be collected on surfaces where varnish, paint, or a coating may come off.

Another, lesser-used option is a vacuum sample. For the most part, vacuum samples have such limitations that either a tape lift or wipe samples would be preferred. However, for sampling something like carpeting, a vacuum sample may be the best option.

Air Sampling

Air sampling for fire-related by-products may sound like a good way to assess potential exposure to hazards in the property. However, due to the timeframe between the fire event and the environmental assessment, it is likely that the contaminants have dissipated or settled out of the air, therefore, making sample collection difficult. Inspectors should make a judgment call on the effectiveness of collecting air samples for fire-related particulates or volatile organic compounds based on the time since the fire, condition of the property during that time, and the fuel sources of the fire.

Some specialized testing that may be done include things like pH testing, VOC and SVOC sampling, heavy metal testing, and more. Depending on the materials that burned in the fire, and the specific concerns an inspector may decide to perform some of these more niche testing methods.

As you can see, there are many different fire testing options. Testing can be performed on the front-end to determine the extent of the damage, or on the back-end to evaluate the restoration work completed.  Contact Indoor Science if you have experienced a fire and are concerned about odors or residues in your property.