Environmental Forensic Investigation of Carbon Monoxide Generation, Exposure Reconstruction, and Industrial Air Quality
Project Overview
Carbon monoxide (CO) exposure incidents represent some of the most challenging environmental forensic investigations because the gas is colorless, odorless, non-irritating, and capable of producing severe health effects before occupants recognize that hazardous conditions exist. Unlike many industrial air contaminants, carbon monoxide can accumulate rapidly within enclosed environments following equipment malfunctions, combustion events, or ventilation failures, creating potentially life-threatening conditions within minutes. Determining the origin of carbon monoxide, reconstructing exposure, evaluating engineering controls, and assessing human health impacts requires integration of environmental chemistry, industrial hygiene, combustion science, engineering analysis, exposure assessment, and toxicology.
The environmental forensic investigation summarized herein evaluated an acute carbon monoxide exposure event that occurred within an industrial water treatment facility containing hazardous gas storage and emergency air treatment equipment. The objective of the investigation was to determine the mechanism responsible for carbon monoxide generation, evaluate the performance of the facility’s gas treatment system, reconstruct worker exposure, estimate airborne carbon monoxide concentrations, and assess the severity of exposure using accepted environmental engineering and industrial hygiene methodologies. Rather than relying exclusively on witness accounts or medical records, investigators integrated engineering documentation, combustion principles, exposure reconstruction, mass balance calculations, toxicological modeling, and publicly available technical information into a comprehensive environmental forensic assessment.
A primary objective of the investigation was to determine whether combustion occurring within an emergency gas treatment system could generate sufficient carbon monoxide to migrate into an adjacent occupied work area. Engineering evaluation focused on combustion conditions, ventilation characteristics, system configuration, airflow pathways, and building geometry to determine whether gases generated within the treatment system could accumulate inside occupied spaces. Historical reconstruction of the incident timeline, combined with engineering analysis, demonstrated that relatively modest rates of carbon monoxide generation within a confined system could produce hazardous airborne concentrations if ventilation pathways allowed reverse airflow into the occupied building.
Another major component of the investigation involved reconstructing worker exposure in the absence of continuous real-time monitoring data. Using accepted environmental engineering methods, investigators applied mass balance calculations, representative building volumes, combustion chemistry, documented incident chronology, and toxicological models to estimate airborne carbon monoxide concentrations over time. Exposure reconstruction was further strengthened through evaluation of observed physiological responses, estimated carboxyhemoglobin (COHb) formation, occupational exposure limits, and federal Acute Exposure Guideline Levels (AEGLs). Integrating these independent analyses provided a scientifically defensible framework for evaluating both the magnitude and duration of exposure while reducing uncertainty associated with limited environmental measurements.
This investigation demonstrates how modern environmental forensic investigations extend beyond identifying the presence of a hazardous gas. By integrating engineering evaluation, industrial hygiene, combustion science, environmental chemistry, exposure reconstruction, contaminant transport, and human health risk assessment, investigators developed a comprehensive scientific understanding of the incident while objectively evaluating contaminant generation, migration, worker exposure, and potential health effects. Such multidisciplinary investigations provide a technically rigorous framework for industrial incident investigations, environmental consulting, occupational exposure assessments, regulatory reviews, and expert witness testimony involving hazardous airborne contaminants.
Chemicals of Concern
Carbon monoxide (CO) was the principal chemical of concern evaluated during this environmental forensic investigation because it was the primary toxic agent responsible for the confined-space exposure event. Carbon monoxide is produced during the incomplete combustion of carbon-containing materials when oxygen availability is insufficient to support complete oxidation to carbon dioxide. Unlike many industrial chemicals, carbon monoxide is colorless, odorless, tasteless, and non-irritating, providing no sensory warning before hazardous concentrations develop. These characteristics make carbon monoxide one of the leading causes of accidental poisoning in occupational settings involving combustion equipment, enclosed spaces, and industrial process failures.
The investigation focused on understanding the mechanism of carbon monoxide generation within an industrial gas treatment system following an internal combustion event. Engineering evaluation demonstrated that oxygen-limited combustion occurring within reactive filtration media created conditions favorable for incomplete combustion and sustained carbon monoxide production. Unlike open flaming combustion, smoldering combustion typically generates significantly greater quantities of carbon monoxide because combustion temperatures remain relatively low while oxygen availability becomes limited. The investigation concluded that relatively small quantities of combustible material undergoing sustained smoldering combustion could generate hazardous carbon monoxide concentrations within an enclosed industrial environment.
A critical aspect of the investigation involved evaluating the environmental behavior of carbon monoxide following its release. Because carbon monoxide is only slightly denser than air, it disperses readily within enclosed spaces and can accumulate rapidly when ventilation is inadequate or airflow pathways allow recirculation of contaminated air. Engineering review of the facility configuration demonstrated that airflow connections between the gas treatment system and the occupied work area created a direct pathway for contaminant migration. Rather than being released into the outdoor environment where atmospheric dilution would occur, carbon monoxide accumulated within the confined workspace, substantially increasing the potential for worker exposure.
The toxicological significance of carbon monoxide arises from its strong affinity for hemoglobin. Once inhaled, carbon monoxide binds with hemoglobin to form carboxyhemoglobin (COHb), reducing the blood’s oxygen-carrying capacity and impairing oxygen delivery to critical organs, including the brain and heart. Because carbon monoxide binds to hemoglobin approximately 200 to 250 times more strongly than oxygen, even relatively short-duration exposures to elevated concentrations can produce clinically significant physiological effects. Symptoms typically progress from headache, dizziness, and fatigue to confusion, impaired coordination, loss of consciousness, and, at sufficiently high exposures, life-threatening toxicity. For this reason, evaluation of estimated COHb levels represented a central component of the exposure reconstruction performed during the investigation. (Industrial Hygiene Assessment; Toxicological Evaluation).
The investigation also evaluated reconstructed airborne carbon monoxide concentrations relative to established occupational and public health guidelines, including OSHA Permissible Exposure Limits (PELs), NIOSH Recommended Exposure Limits (RELs), Immediately Dangerous to Life or Health (IDLH) values, and the U.S. Environmental Protection Agency’s Acute Exposure Guideline Levels (AEGLs). Comparing reconstructed exposures with these scientifically established benchmarks provided an objective framework for evaluating exposure severity while placing the reconstructed concentrations within the context of accepted industrial hygiene and toxicological standards. (Industrial Hygiene Assessment; Toxicological Evaluation).
Methods
The environmental forensic investigation employed a multidisciplinary methodology integrating historical document review, engineering evaluation, industrial hygiene, combustion science, environmental chemistry, exposure reconstruction, mass balance analysis, toxicological modeling, and regulatory assessment. Because direct environmental monitoring data were limited during the initial stages of the incident, investigators relied on multiple independent lines of scientific evidence to reconstruct the sequence of events, evaluate carbon monoxide generation, estimate airborne concentrations, and assess potential human exposure. This weight-of-evidence approach is widely accepted in environmental forensics and industrial hygiene investigations where direct measurements are unavailable or incomplete.
The investigation began with a comprehensive review of available engineering documentation, incident records, facility information, publicly available emergency response reports, and technical literature describing the operation of industrial gas treatment systems. Historical reconstruction focused on identifying the sequence of equipment operation, combustion initiation, emergency response activities, and worker exposure. Particular attention was given to evaluating the physical relationship between the gas treatment equipment and the occupied workspace, allowing investigators to determine whether system configuration and airflow pathways could have permitted contaminated air to migrate into areas occupied by personnel.
A central component of the investigation involved evaluating the mechanism of carbon monoxide generation using accepted principles of combustion science and environmental engineering. Investigators examined the conditions necessary for incomplete combustion, including oxygen-limited environments, confined combustion zones, and sustained smoldering of carbon-containing materials. Engineering analyses assessed whether the reported combustion conditions were capable of generating carbon monoxide at rates sufficient to create hazardous concentrations within the occupied building. This evaluation incorporated published combustion literature together with engineering principles governing heat transfer, airflow, and confined-space combustion.
Exposure reconstruction was performed using mass balance calculations commonly employed in environmental engineering and industrial hygiene investigations. Representative building dimensions, estimated ventilation characteristics, combustion source strength, and carbon monoxide generation rates were combined to estimate airborne concentrations over time. Investigators evaluated the quantity of carbon monoxide required to produce hazardous indoor concentrations together with the corresponding amount of combustible material necessary to sustain those releases. These engineering calculations demonstrated that relatively modest rates of carbon monoxide generation could produce dangerous conditions within a confined workspace when ventilation was insufficient to dilute or remove contaminated air.
Human exposure was evaluated using established carboxyhemoglobin (COHb) toxicokinetic modeling developed by the U.S. Environmental Protection Agency. Estimated airborne carbon monoxide concentrations and documented exposure durations were incorporated into accepted physiological models to estimate blood carboxyhemoglobin concentrations likely to occur during the incident. These modeled values were then compared with reported clinical observations, occupational exposure standards, EPA Acute Exposure Guideline Levels (AEGLs), OSHA Permissible Exposure Limits (PELs), NIOSH Recommended Exposure Limits (RELs), and Immediately Dangerous to Life or Health (IDLH) concentrations. Integrating toxicological modeling with engineering analyses provided an independent means of evaluating the plausibility and severity of reconstructed exposure conditions. (Industrial Hygiene Assessment; Toxicological Evaluation).
Finally, all engineering analyses, combustion evaluations, exposure reconstruction calculations, toxicological modeling, incident chronology, and industrial hygiene information were synthesized into a unified environmental forensic investigation. Rather than relying on a single analytical method or isolated observation, investigators compared multiple independent sources of scientific evidence to determine whether the reconstructed exposure scenario was consistent with the documented sequence of events and established principles of environmental chemistry, industrial ventilation, combustion science, and human toxicology. This multidisciplinary methodology provided a technically rigorous and scientifically defensible framework for evaluating confined-space carbon monoxide exposure events while supporting environmental consulting, occupational exposure investigations, industrial incident analysis, and expert witness testimony.
Results
The environmental forensic investigation demonstrated that the confined-space exposure event was consistent with sustained carbon monoxide generation originating within an industrial gas treatment system rather than an external environmental release. Review of engineering documentation, incident chronology, combustion principles, exposure reconstruction, and toxicological evaluation indicated that carbon monoxide was generated through incomplete combustion occurring within reactive filtration media under oxygen-limited conditions. Engineering analyses further demonstrated that the physical configuration of the air treatment system provided a direct pathway through which carbon monoxide could migrate into an adjacent occupied workspace. Collectively, these findings established a scientifically plausible sequence linking combustion, contaminant generation, indoor migration, and worker exposure through multiple independent lines of evidence.
Engineering analyses demonstrated that only a relatively small amount of combustible material undergoing sustained smoldering combustion would have been required to produce hazardous indoor carbon monoxide concentrations. Mass balance calculations indicated that carbon monoxide generation rates commonly associated with confined smoldering fires were sufficient to produce elevated concentrations within the enclosed workspace over a relatively short period of time. Because the affected work area represented a confined indoor environment with direct airflow connections to the combustion source, relatively modest carbon monoxide generation rates could produce rapidly increasing airborne concentrations in the absence of effective ventilation or source isolation. These engineering calculations were consistent with accepted principles of combustion chemistry, industrial ventilation, and environmental engineering.
Reconstruction of the incident timeline demonstrated that worker exposure likely occurred over an extended period rather than during a single instantaneous release. Review of emergency response records and engineering documentation indicated that combustion continued while emergency response activities were underway, allowing carbon monoxide concentrations to persist and potentially increase until the combustion source was controlled. The progression of documented medical events was consistent with a sustained exposure scenario in which airborne concentrations increased over time within the occupied workspace. Historical reconstruction therefore supported the conclusion that the incident involved continuous contaminant generation and accumulation rather than a brief release followed by rapid ventilation.
Toxicological evaluation further supported the engineering reconstruction. Estimated airborne carbon monoxide concentrations, when evaluated using established carboxyhemoglobin (COHb) formation models developed by the U.S. Environmental Protection Agency, produced predicted blood COHb levels consistent with the reported progression of clinical symptoms observed during the incident. Comparison of reconstructed exposures with OSHA Permissible Exposure Limits (PELs), NIOSH Recommended Exposure Limits (RELs), Immediately Dangerous to Life or Health (IDLH) concentrations, and EPA Acute Exposure Guideline Levels (AEGLs) demonstrated that estimated exposure conditions substantially exceeded occupational exposure guidelines associated with routine workplace operations. These comparisons provided an objective toxicological framework for interpreting the reconstructed exposure scenario using nationally recognized health-based standards. (Industrial Hygiene Assessment; Toxicological Evaluation).
An important finding of the investigation was that the incident represented a localized occupational exposure event rather than a broader environmental release affecting the surrounding community. Engineering documentation and incident information indicated that hazardous carbon monoxide concentrations were confined primarily to the enclosed workspace because the source of combustion remained within the industrial gas treatment system and exposure occurred through internal airflow pathways. This distinction significantly influenced both the exposure assessment and the environmental forensic evaluation by focusing the investigation on confined-space ventilation, engineering controls, contaminant migration within the facility, and worker exposure rather than off-site atmospheric dispersion.
Taken together, the engineering evaluation, combustion analysis, exposure reconstruction, mass balance calculations, toxicological modeling, and historical incident reconstruction demonstrated the value of integrating multiple independent scientific disciplines into a unified environmental forensic investigation. Rather than relying solely upon direct monitoring measurements or individual witness observations, investigators synthesized engineering principles, environmental chemistry, industrial hygiene, exposure science, and toxicology to objectively evaluate contaminant generation, transport, human exposure, and potential health effects. This multidisciplinary approach substantially strengthened the technical evaluation while reducing uncertainty associated with any single analytical method or individual dataset.
Conclusions
This environmental forensic investigation demonstrates that evaluating confined-space carbon monoxide exposure events requires substantially more than documenting the presence of a hazardous gas or comparing measured concentrations with occupational exposure limits. A scientifically defensible investigation requires integration of engineering evaluation, industrial hygiene, combustion science, environmental chemistry, exposure reconstruction, toxicology, and historical incident reconstruction to objectively determine how carbon monoxide was generated, transported, accumulated, and ultimately inhaled by exposed workers. By synthesizing multiple independent sources of technical information, investigators developed a comprehensive understanding of the incident while reducing uncertainty associated with limited environmental monitoring data.
The investigation further illustrates the importance of applying engineering-based exposure reconstruction when direct environmental measurements are unavailable or incomplete. Through mass balance calculations, combustion analysis, ventilation evaluation, and toxicokinetic modeling, investigators reconstructed airborne carbon monoxide concentrations and estimated internal carboxyhemoglobin (COHb) levels using scientifically accepted methodologies. These analyses demonstrated how relatively small quantities of combustible material undergoing sustained smoldering combustion within an enclosed system could generate hazardous carbon monoxide concentrations capable of producing serious physiological effects. Incorporating engineering calculations with toxicological modeling provided an objective framework for evaluating both the magnitude and duration of worker exposure.
Another significant finding was the critical role of facility design and ventilation pathways in determining contaminant transport. Rather than dispersing into the outdoor environment, carbon monoxide generated within the industrial gas treatment system migrated through interconnected airflow pathways into an occupied workspace where it accumulated over time. This confined-space migration mechanism fundamentally influenced the exposure scenario and demonstrated how engineering design characteristics can significantly affect contaminant behavior independent of the amount of carbon monoxide generated. Evaluating ventilation systems, airflow pathways, equipment configuration, and building geometry therefore represented an essential component of the environmental forensic investigation and highlighted the importance of engineering controls in preventing hazardous occupational exposures. (Engineering Evaluation; Industrial Hygiene Assessment).
More broadly, this investigation demonstrates how modern environmental forensic investigations integrate environmental consulting, industrial hygiene, environmental chemistry, combustion science, engineering analysis, exposure science, toxicology, and human health risk assessment to objectively evaluate complex occupational exposure events. Combining contaminant fate and transport, mass balance analysis, exposure reconstruction, toxicokinetic modeling, and multiple independent lines of evidence provides a scientifically rigorous framework for supporting industrial incident investigations, environmental litigation, regulatory reviews, occupational health evaluations, and expert witness testimony. As industrial facilities continue to incorporate increasingly sophisticated gas treatment and process control systems, multidisciplinary environmental forensic investigations remain essential for objectively evaluating hazardous gas releases, reconstructing historical exposures, and identifying the engineering and environmental factors that contribute to confined-space chemical exposure events.
This investigation was conducted under the direction of Dr. Paul Rosenfeld, an environmental scientist and environmental forensic expert with extensive experience in environmental exposure assessment, toxicology, air quality, environmental fate and transport, risk assessment, and environmental forensics. Through RoseyFields LLC, Dr. Rosenfeld provides scientific consulting, environmental forensic analysis, regulatory support, and expert witness services involving environmental contamination, human exposure, and public health. His technical oversight helped ensure that the methodologies, scientific interpretations, and conclusions presented in this case study are consistent with accepted scientific principles and current best practices.