DUCTLESS FUME HOODS, according to the American Chemical Society Chemical Health and Safety Committee, are devices, which recirculate air from the hood or enclosure back into the laboratory environment. The air may be filtered in some manner or unfiltered. They are unique in that they do not require any exhaust ducting, have built in blowers, do not upset any room air balances, and can easily be installed by two-three persons. For many laboratory operations involving volatile chemicals, ductless hoods are inappropriate and may present serious dangers.
The NFPA Standard 45 for Fire Protection for Laboratories Using Chemicals states that "air exhausted from laboratory hoods or other special local exhaust systems shall not be recirculated. In addition, ductless fume hoods should meet all other standards for fume hoods, such as airfoil use, containment criteria, and air movement.” ANSI further indicates that if ductless hoods are used for toxic, or volatile chemicals they must have adequate adsorption characteristics, that air monitoring after the filter be conducted to determine if the filter loses its effectiveness, and if the filter fails that air be directed outside or to a second filter. Today, particulate filters have a retention efficiency of 0.3 micron-sized particles of up to 99.9 percent efficiency. However, these filters do not withstand all modes of chemical attack, are generally not resistant to heat, and can develop small leaks between the filter and the filter-housing unit. Filters must be changed regularly to meet the above qualities.
Science experiments in the classroom are a necessary part of the science curriculum. Hands on experiments enhance the learning process of students. These experiments either smoke, produce heat, release toxic vapors or in worst case explode. As an educator you are exposed to these chemicals countless more times than the student. Preparation, demonstration and cleanup are peak exposure times for you, the educator. Protect yourself from these hazards with a ductless chemical fume hood.
Airclean Systems, one of the U.S. pioneers in Ductless Workstations, says of such technology in you classroom:
AirClean® Systems ductless classroom demonstration workstations comply with the following standards and governmental agencies.