Evaluating Chronic Carbon Monoxide Exposures: An Engineering Fundamentals Approach

摘要

Acute toxicity results from exposure to a toxin either from a single event or from multiple events within a short time span, usually less than 24 hours. On the other hand, chronic toxicity stems from repeated exposures at lower levels over a longer period. Chronic exposure to carbon monoxide (CO) reportedly manifests in a confusing array of unrelated symptoms and is difficult to diagnose. The source of CO in a chronic exposure incident is typically a fuel-burning appliance in a residence or a workplace setting. An engineering analysis of the potential source and the surroundings can provide valuable insight on the likelihood of the appliance as a viable source. Such analyses can yield-within a reasonable degree of engineering certainty-conservative estimates of the level the individual was exposed to, and the duration and frequency of each exposure. In this paper, we present a transient material balance to determine volume-averaged, time-dependent concentrations within a residence. We highlight the techniques used to estimate each term of the material balance equation as they apply to a real-world scenario. For example, we employed computational fluid dynamics as well as visual examination of a gas-fired appliance to evaluate the magnitude of a source term in the material balance.