A ductless fume hood is a self-contained laboratory enclosure that passes contaminated air through filters before returning the air directly back to the laboratory. Ductless fume hoods are not connected to an exhaust system, so they rely upon activated carbon filters to remove hazardous fumes and vapors resulting from chemicals used on the work surface to protect personnel, processes and the laboratory environment. It is important to use the proper filter for the class of chemicals used in the application. For assistance in determining product compatibility for your chemical application, please complete the Air Science SEFA compatibility form.
The effectiveness of a ductless fume hood depends upon the quality of the activated carbon filters packed into the filter housing. Activated carbon granules serve as the primary line of defense against vapors emitted from the work surface. Exposure to hazardous fumes can pose significant health risks to laboratory personnel even at relatively low volumes over time. However, it is necessary to understand that all carbon filters are not the same. Carbon filter selection based upon price alone can pose a danger to lab personnel and the environment. Knowing what to look for when choosing a replacement carbon filter is critical to laboratory safety.
High-quality activated carbon filters used in ductless enclosures are formulated to protect against specific chemical hazards and remain effective within the threshold limit value (TLV) of your application. Ductless fume hood manufacturers define the replacement activated carbon filter specifications that are necessary to ensure safe operation of the ductless enclosure. Regardless of the manufacturer, your ductless enclosure includes filter requirements that are essential for safe operation. Replacement filters should be acquired only from reputable manufacturers. Air Science is a source for high-quality activated carbon filters through Filtco Filters, a producer of replacement carbon filters that meet the size specifications of more than 25 major ductless enclosure manufacturers worldwide.
To protect laboratory personnel from harmful vapors generated on the work surface, carbon filters must be replaced on a regular schedule to avoid the effects of over-saturation. Even small levels of hazardous vapors that pass through old, expended filters pose significant risk. As important as a filter replacement schedule is for continued laboratory safety, the benefits are dependent upon initial filter quality. Effective filter adsorption and chemisorption are entirely dependent on filter quality. Additionally, the ability of a filter to function safely and efficiently depends on a number of factors including temperature, humidity, residence time, filter age, evaporation rate and chemical concentration.
While cheap replacement filters may seem like a good idea due to the cost savings involved, low-quality replacement filters, including aftermarket, homemade or do-it-yourself carbon filters can be dangerous. Cheap replacement filters not only jeopardize safety by creating undetected workplace hazards, but they can also void the manufacturer?s warranty of your equipment. Aftermarket, homemade or filters of questionable quality pose significant risks to laboratory personnel. While these filters may be cheaper, they are often made using inferior carbon packing that will not protect against chemical hazards. For example, low-quality carbon filters are often filled with common charcoal used in fish tank filters. This carbon is not chemically prepared to contain chemical vapors.
Off-brand replacement carbon filters can pose significant dangers if the manufacturing origin and quality control does not meet industry standards for use in a ductless enclosure. Efficient filter frame design, proper loose carbon granule preparation and continuity in frame filling are critical to safe ductless fume hood operation. From facility managers to end users, all personnel must be confident in the efficacy of any replacement filter to protect against the hazardous fumes and vapors that the fume hood is designed to contain.
Learn how to identify quality replacement carbon filters and read more about how activated carbon filters function in the Air Science free ebook Filter Integrity: Why Do-It-Yourself Replacement Carbon Filters Can Endanger Lab and Personnel Safety.
Resources
Enhanced Filtration Technology
Adsorption vs. Absorption: The Difference for Carbon Filters
