Controlled atmosphere cabinet has enclosure (110;210) with means providing visibility (110F; 210F) of its interior from outside, gas supply (113-116, 212-216) for desired or target composition of internal atmosphere, controlled lock-type access (112) for manual introduction and removal of items, and hand/arm access port provision (111A, B; 211A, B) for manipulation of said samples in the cabinet. Gas supply associated control means (230-240) serves during use of the cabinet (other than normal atmosphere augmenting in use of the lock-type access) for additional gas supply further to correct or compensate for effects actually or potentially adverse to maintaining the desired or target internal atmosphere composition, via operator-actuated input means (121t, 123; 222) and/or means (122, 124, 139; 225) for sensing prescribed conditions to which the control means is responsive for said additional gas supply.