Ductless laboratory hood apparatus

A ductless laboratory hood apparatus for disposition in an ambient laboratory environment for containment of chemical reactions, experiments and other laboratory processes which generate toxic or noxious chemical contaminants in the presence of flames or heat, comprising:

• a housing defining interiorly a work chamber suitable for performance therein of said laboratory processes and a filtration chamber, the housing substantially fully enclosing the work chamber except for an access window opening from the laboratory environment into the work chamber, the housing further including an exhaust outlet opening from the filtration chamber into the laboratory environment,
• a filter system disposed within the housing between the work and filtration chambers,
• an air circulation system for creating and directing an airstream to flow from the laboratory environment inwardly through the access window into the work chamber, from the work chamber upwardly through the filter system into the filtration chamber, and from the filtration chamber through the exhaust outlet into the laboratory environment, for containing and preventing toxic or noxious chemical contaminants from passage from the work chamber into the laboratory environment through the access window,
• the filter system comprising a flame attenuation filter and a main filter arranged closely adjacent one another with the flame attenuation filter disposed between the work chamber and the main filter for upward flow of the airstream in sequence first through the flame attenuation filter and then directly through the main filter, wherein:
• the main filter being of a sufficiently high efficiency and capacity for removing substantially all toxic or noxious chemical contaminants from the airstream to render the airstream safe for human consumption after exhaust into the laboratory environment,
• the main filter comprising a flammable material that is damaged if exposed directly to laboratory processes generating flames or heat, and
• the flame attenuation filter comprising an inflammable heat-resistant porous ceramic foam filtration material disposed to intercept and attenuate flames or heat generated by laboratory processes to prevent the flames or heat from reaching the main filter, thereby preventing damage of the main filter.