He pū kāwhe tonu ngā pū whēao i te tahuhu, me te tirohanga o te pū ki runga i te puaki. I te wā e kai ana i te whakamahinga i te hā, ka taea te whakauru i tētahi kape ki runga i te puaki hei tiaki i a ia i te wā e kore ai e whakamahi ana, arā, mēnā ka tuwhera te pū. Inahea ko te kape, he poraka rānei hei tiaki i te puaki. I te Tira Ataata o te Pōneke, he ingoa tonu ngā hononga puaki, nā te Rōpū Whēako Whēao (CGA) i whakarite i ngā tohutohu mō ngā hono hei whakamahia mo ngā hā. Hei tauira, he "CGA 580" te hono puaki i roto i tētahi pū argon. No reira, he wā kei raro i ngā hā paihere, ka whakamahia ngā hono CGA-DISS ("Diameter Index Safety System").