PH helmet

It featured two mica eyepieces instead of the single visor of its predecessor, and added an exhale valve fed from a metal tube which the wearer held in his mouth.

It had flannel layers of cloth-dipped in sodium phenolate and glycerin and protected against chlorine and phosgene, but not against tear gas.

The PH Helmet (Phenate Hexamine) replaced it in January 1916, and added hexamethylene tetramine, which greatly improved protection against phosgene[3] and added protection against hydrocyanic acid.

[4] Around 14 million were made and it remained in service until the end of the war by which time it was relegated to second line use.

It was finally superseded by the Small box respirator in 1916, which was much more satisfactory against high concentrations of phosgene or lachrymators.