Realistically, the filter capacity estimates are recommended to be ~1/3 of calculated theoretical values. Unpredictable variables can affect the actual results. If you've spent time in a chemistry laboratory, you'll realize that the theoretical values obtained through stoichiometry and other calculations aren’t precisely yielded in the real world. As an example, if a carbon filter has a filter-weight capacity for xylene of 27.6%, you could theoretically trap 27.6 grams of xylene in 100 grams of its carbon. This can be converted to volume by dividing the chemical weight by the chemical’s specific gravity (27.6 grams / 0.86 grams/mL = 32 mLs is retained on a 100 gram filter).Īre the capacities provided theoretical or realistic values? This is a “capacity by weight” ratio that can be used to calculate chemical volume based on filter size. Whereas, the same filter may be rated to hold 60mLs of isopropyl alcohol, then the theoretical volume capacity of that filter for isopropyl alcohol is 60mLs.Ĭarbon substrate manufacturers and filter manufacturers may also choose to express a filter’s capacity for any given chemical by providing a filter-weight capacity percentage. For example, a filter is rated to hold 250mLs of xylene, then the theoretical volume capacity of that filter for xylene is 250mLs. A filter’s capacity is often expressed as a chemical-specific theoretical volume that it has the capacity to retain before saturation for that chemical. Therefore, it is critical to understand how long carbon filters should last, or at the very least, to understand when your filters become saturated, and need replacement.Ĭarbon filter capacity is expressed in several different ways, but two methods are most common.įilter manufacturers typically list dedicated catalog numbers for filters of standard nominal sizes. In order to maintain this safe and clean environment, filtration systems should be monitored, and the filters should be replaced when necessary. Air filtration by adsorption is the process many laboratories use to provide a safe and clean environment for their personnel. Carbon media is an effective adsorbent because it is a highly porous material and provides a significantly large surface area to which contaminants may adsorb. Activated and Impregnated Carbon Media can be effective at filtering vapor contaminants out of the airstream by a process called adsorption.
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