When the 2025 Los Angeles wildfires swept through communities across the region, residents faced widespread physical damage, as well as persistent chemical contamination in the air, on surfaces, and in soil.
In response, Leslie Silva—an applications scientist at Syft Technologies—initiated an investigation into volatile organic compound (VOC) contamination in homes, insulation, and soil using selected ion flow tube mass spectrometry (SIFT-MS), a technique capable of real-time, in situ analysis.
Her work highlights potential exposure pathways to harmful VOCs that may persist in indoor environments after wildfire events. It also underscores the importance of characterizing indoor VOC concentrations, as chronic exposure to elevated levels of compounds such as benzene and formaldehyde has been associated with respiratory dysfunction, neurotoxicity, and increased cancer risk.
From Concern to Collection: Initiating a Real-Time VOC Study
Silva’s study of VOC contamination was prompted by both scientific and personal interest. “I live in LA. I have a young family, and I feel like everyone had the same concerns and worries about exposure to smoke and the lingering contaminants in homes after the fires,” she explains.
With access to a SIFT-MS instrument at the University of California, Los Angeles (UCLA) Molecular Instrumentation core facility, she saw an opportunity to provide real-time VOC data that could help residents make more informed decisions.
Silva analyzed samples from indoor air, insulation, and soil collected from various locations, using lab-based SIFT-MS to enable direct analysis of enclosed and built environments. This was especially important for assessing VOC contamination in spaces where residents were still living or hoping to return.
To capture a full picture of the VOC contamination, Silva designed targeted sampling protocols for each type of material:
- Air: Samples were collected using 1-liter Tedlar bags from both indoor and outdoor environments.
- Insulation: 0.2 grams of insulation was placed into 20 mL headspace vials and incubated at 70°C for 20 minutes prior to analysis.
- Soil sampling: 27 total samples were collected and spatially categorized:
- Burned: Directly impacted by fire or visibly charred.
- Adjacent: Within 10 feet of burned areas.
- Close: Located 3–5 miles from fire zones.
- Control: Over 20 miles away, in Studio City.
These sampling approaches allowed Silva to compare VOC levels across environments and materials, providing essential spatial and compositional context for interpreting contamination patterns.
VOC Findings Across Air, Insulation, and Soil
Silva’s study provides a detailed picture of the chemical residues left behind in different materials. The investigation followed a targeted approach, focusing on a predefined list of approximately 25 VOCs identified as relevant based on prior wildfire studies.
Contaminants varied by sample type:
Indoor Air
Elevated levels of xylenes, ethylbenzene, and trimethylbenzene were detected in smoke-damaged homes. One residence downwind from a burning structure showed trimethylbenzene concentrations up to 5.8 parts per billion (ppb), while the combined levels of xylenes and ethylbenzene exceeded 50 ppb.
Notably, formaldehyde levels were elevated in nearly all indoor samples, reaching up to 30 ppb. By comparison, the United States Environmental Protection Agency (EPA) reference concentration (RfC) for chronic exposure to formaldehyde is 6 ppb, and the California Office of Environmental Health Hazard Assessment (OEHHA) indicates 7 ppb. Only one home under construction, lacking furnishings, registered substantially lower levels. “It sheds light on what is off-gassing in your home, for example, your carpets and couches,” Silva remarks.
Silva also notes that an analytical challenge she encountered involved Tedlar bags used for air sampling, which are known to be contaminated with dimethylacetamide. “The 13C isotope of dimethylacetamide has the same mass as dioxane, unfortunately,” she explained. As a result, dioxane data were excluded from the air sample analysis.
Insulation
Elevated VOCs in insulation included acetaldehyde, benzene, xylene, dioxane, camphor, and furan. In some headspace measurements, acetaldehyde and camphor exceeded 100 ppb and 20 ppb by volume, respectively. For context, acetaldehyde’s EPA RfC is 0.005 ppb. Benzene, a known carcinogen with an RfC of about 9 ppb, was also present.
Soil
Soils, particularly in burned areas, showed the broadest range of VOC contamination. Detected compounds included alkanes, isoprene, toluene, and isopentane, with significant variation between burned, adjacent, and control sites. Acetaldehyde and alkanes showed the highest VOC concentrations among the soil samples collected from burned areas, highlighting the severity of contamination observed in those zones.
While direct health benchmarks for VOCs in soil headspace are less established than for air, these results suggest both contamination and the potential for VOC re-emission under warm or poorly ventilated conditions.
Overall, these findings underscore the need for a comprehensive understanding of post-fire contamination.
Why SIFT-MS Was Selected for This Application
The analytical capabilities of SIFT-MS significantly contribute to the success of the study. “SIFT-MS offers the ability to analyze samples in real time from whole air with no sample prep. This would make it faster than something like GC-MS... just as sensitive, if not more sensitive,” notes Silva.
She emphasizes one of the key analytical strengths: “With SIFT-MS, you have multiple reagent ions available to you at all times. So you end up with several independent measurements of the same VOC.” These reagent ions (H3O+, NO+, O2+) are particularly useful in chemically complex matrices, such as insulation and soil.
“We saw a lot of alkanes present, especially in soil samples, and they only react with O2+,” Silva explains. “So having that reagent ion available along with the others was important, because we were able to see those and see how elevated they were.”
SIFT-MS is also highly sensitive, with a wide dynamic range. Silva notes that the instrument can detect compounds in the low to mid-part-per-trillion (ppt) range, up to high ppm concentrations, depending on the VOC.
Environmental Variables: Temperature, Ventilation, and Furnishings
Beyond identifying contaminants, Silva also investigated how environmental conditions, such as heat and ventilation, affected the persistence of these contaminants.
Silva monitored a sealed home in Altadena where power and HVAC had been off for weeks. The home showed steadily increasing VOC concentrations as indoor temperatures rose. After airing it out and resampling, VOC levels dropped, only to spike again when the windows were closed during a warm weekend.
Quantitative measurements showed that acetaldehyde levels increased noticeably as indoor temperatures rose from 30°C to 50°C. Similar temperature-driven trends were observed for trimethylbenzene and other VOCs.
“Ventilation lowers airborne VOC levels through dilution, but many of these compounds remain embedded in the home’s materials,” Silva explains. “I think it’s mostly soft goods, such as couches and cushions, that are causing a lot of these emissions.”
These results reinforce the role of temperature and ventilation in influencing VOC persistence and highlight how soft furnishings can trap and gradually release VOCs over time, making airflow a critical factor in post-fire remediation.
Regulatory Gaps and Remediation Outcomes
While much of the focus in wildfire recovery centers on indoor air quality, Silva’s study reveals that soil also plays a significant role in post-fire exposure. Soil samples, even those from areas surrounding remediated properties, show the presence of persistent VOCs. Encouragingly, FEMA’s recommended 6-inch soil removal appeared to be effective in reducing VOC levels in remediated areas. However, surrounding wildland soils remained contaminated, raising concerns about cross-contamination and reabsorption into cleaned zones over time.
Understanding when to replace smoke-damaged insulation is also important. “The current test that environmental consultants are performing in these homes to see if insulation should be replaced is a smell test, which is very subjective,” Silva explains. She notes that VOCs, such as camphor, furan, and BTEX compounds (benzene, toluene, ethylbenzene, and xylenes), could serve as objective chemical markers to inform cleanup standards.
Ongoing Research and Expanding the Field
Silva and her collaborators are continuing full-scan analysis to explore VOCs beyond their initial target list. “That full scan analysis is still ongoing to see if there’s anything that I missed,” she says. The untargeted approach broadens detection to potentially overlooked contaminants not captured in the original focus.
She also plans to return to several homes post-remediation to assess VOC changes over time. Collaborators at UCLA are examining the off-gassing from smoke-damaged belongings, while other researchers in the field are burning materials such as TV plastics and roofing shingles to create more accurate emission profiles.
Future research may also explore the impact of burning modern building components, such as solar panels and electric vehicles, which were not yet included in this study but are increasingly common in residential areas. Additional studies may address method sensitivity limits and refine calibration models across materials to support long-term monitoring and standardization.
Conclusion: Monitoring the Unseen
Silva’s study highlights the practical advantages of SIFT-MS in disaster response, delivering rapid, real-time data with the sensitivity and selectivity needed to assess chemically complex environments. These capabilities make it especially valuable in post-fire scenarios where timing and precision are critical.
As wildfires become more frequent and severe due to climate change, the ability to monitor VOCs in real time will play an increasingly important role in both emergency response and long-term public health planning. Silva’s work demonstrates how direct access to this technology can support faster decision-making and more informed remediation strategies.
