Zida zowopsa sizimasiyanitsidwa ngati gulu A kapena B koma ndi zoopsa zake, monga zinthu zowononga, mpweya wapoizoni, ndi madzi oyaka.
Magulu a kalasi A ndi B adafotokozedwa mu GB50160-2008 “Petrochemical Enterprises Fire Safety Design Miyezo.”
Pentane, ndi kung'anima kwa -40 ℃ ndi kuphulika kwapansi malire a 1.7%, amaikidwa m'gulu la mankhwala owopsa a Gulu A.