to the leg in order to permit ingress and egress from the unit 10 a passageway 70 is provided in one of the wall structure sheets 50 56 it being noted that the bottom of the passageway is above bottom panel 42 to retain the liquid holding capacity of the basin floor 38 also other similar passageways can be provided in other wall structure sheets such as shown in phantom in fig1 depending upon the desired use of the unit in question in preferred embodiments perforations may be made in portions of wall structure 40 so that additional passageways may be formed by punching out the perforated wall portions providing perforated wall sections enables the unit 10 to be used in a staged decontamination procedure in coordination with additional units the erection of the unit 10 is very easy and can be accomplished in a matter of a very few minutes as delivered the unit is housed within a flexible bag containing the frame 12 in its collapsed condition as well as the enclosure 14 the first step is to erect the frame 12 involving separation of the scissor linkages 20 by manually shifting the legs 16 until the slide brackets 24 move upwardly and the pins 19 a are received within the bracket apertures 25 next the legs 15 are elongated by extension of the sections 16 b relative to the upper section.