Analysis of respiratory filters by the Wheeler-Jonasequation
Abstract: Within the Swedish Armed Forces different types of filters are used in respirators, vehicles and naval ships to protect against chemical agents. The filters are to protect against a variety of chemicals. The Swedish armed forces has a need for a predictive model describing breakthrough times through such filters. There are several known models for carbon filtering and the one most used is the Wheeler-Jonas (WJ) equation[3]. In this thesis focus lies on filters made with activated carbon, the kind of filters used in gas masks and especially "skyddsfilter 90". The task is to find a model among the existing models for carbon filtering breakthrough times and determine if it can predict penetration times of different compounds both organic and inorganic in "skyddsfilter 90" and if so suggestsuch a model. The time of resistance in a filter depends on both the type of chemical, concentration and the rate of flow through the filter. These are some of the parameters used in the WJ equation. The investigation will show that the WJ equation is applicable to most of the chemical agents that is of interest to military use and that it can be used for carbon filters of varying size. However for filters made with different materials further research is needed. The work demonstrates how to use the model correctly, how to testits applicability and when possible calculations based on given data is performed.
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