PURPOSE: To provide a space-saving laboratory wherein a reseacher and a third person are protected against an emergent explosion accident.

CONSTITUTION: This laboratory is provided with reinforced concrete for forming a longitudinal and transverse walls 5, floor and ceiling; a floor duct and a ceiling gallery for ventilating the inside of room with outside air; a steel door 9 for opening/closing a gateway 8; a monitor window 10 furnished with a transparent board and equipped in a rear wall; and a chimney part projected upward from an opening of the ceiling, of which a roof for covering a top thereof is opened in the case of explosion of substance such as high pressure gas. A longitudinal wall 14a and a transverse wall 14b are provided between the gateway 8 and a passageway 2 communicated with the forward thereof. Laboratories 1, 1 adjoining to each other are partitioned by a steel suspension door 17 which is movable and can be drawn to the outside of the laboratory.