Original Item. One-of-a-Kind. This is an exceptionally scarce surviving British WWI Hypo Helmet, officially known as the British Smoke Helmet, representing one of the earliest purpose-designed British protective hoods issued in response to chemical warfare on the Western Front. This heavily age-worn example retains its characteristic single rectangular mica eyepiece together with an unusual series of rear ventilation-style grommets and two later identification tags, including a July 1942 OHMS tag describing it as a First World War tear-gas helmet. The hood presently measures approximately 16 1/2 inches tall by 13 1/2 inches wide when laid flat and may have been shortened from its original dimensions.

The Hypo Helmet was developed in 1915 by Captain Cluny Macpherson, Medical Officer of the Newfoundland Regiment, following the introduction of chlorine gas on the Western Front. Imperial War Museums identifies the device as the British Smoke Helmet and records Macpherson as its inventor. It represented a major improvement over the earlier improvised veil respirators by enclosing the entire head inside a chemically treated fabric hood and protecting the eyes behind a transparent viewing window.

The defining feature of the earliest Hypo pattern was a single rectangular transparent eyepiece, initially made from mica. Surviving museum examples retain this same broad single viewing aperture, and the Imperial War Museums specifically describes the Hypo Helmet as fitted with a rectangular mica eyepiece. The Australian War Memorial likewise documents surviving examples with a single large rectangular viewing panel, noting that early mica windows were extremely brittle and prone to cracking.

The eyepiece on this example shows substantial age deterioration. The mica is heavily cracked, and small sections have broken away, exposing portions of the underlying stitching and edge construction. Old tape repairs have been applied across several of the cracks, apparently in an effort to stabilize the fragile viewing panel. These repairs should be left undisturbed, as both the mica and surrounding material are now extremely delicate.

The exterior of the hood has developed a dark, nearly blackened surface finish that is now extensively cracking and flaking. This may result from the original chemical treatment, subsequent preservation treatment, prolonged storage conditions, or a combination of factors. Early Hypo helmets were made from chemically impregnated flannel or similar woolen fabric, and surviving examples frequently exhibit staining or discoloration associated with their chemical treatment. The present black appearance should therefore be described as an observed condition feature rather than used by itself to identify a particular production variation.

The hood has three vertical seams on the back, with a stitched quilted style fabric attached along the interior below where the head would be.

The back of the helmet has an interesting liftable canvas flap covering a zig-zag row of thirteen grommets grommets for airflow, with six on one side of the seam and seven on the other. Attached through these holes are two very old tags, one being fabric with the stamped inscription HELMET, TEAR GAS. The other tag is interesting in that it is a 7-42 (July 1942) dated OHMS tag (On His Majesty's Service), which is inscribed:

HELMET
TEAR GAS
1914-18 WAR

On His Majesty's Service was an official franking formerly seen on correspondence from government departments in the United Kingdom. This would denote that the hood was government property at one point during the World War II period.

A few small pieces of the mica eyepiece have broken off as shown, but the patina across the hood gives it an outstanding look. From the way the canvas has been finished, this is likely one of the later Hypo helmet variants applied with chemicals meant to defeat other respiratory poison gases used, and if the attached tags are to be believed, it was meant to be worn against tear gas. The helmet may have been cut down from its original length, and in its current form measures 16 ½” tall and is 13 ½” across when laid flat.

The Hypo Helmet was only a brief stage in the rapid development of British anti-gas equipment. Its simple impregnated fabric construction was soon followed by improved P and PH helmets using different chemical treatments and additional breathing arrangements, and ultimately by more sophisticated respirators with separate filter canisters. The early Hypo nevertheless represents one of the first standardized British attempts to provide the entire soldier population with purpose-built protection against poison gas.

This example is particularly significant for the survival of its single early-pattern mica eyepiece, heavily aged chemically treated hood, rear grommet arrangement, and provenance tags. The cracked and partly missing mica, old tape repairs, deteriorating exterior finish, and possible shortening are substantial condition issues, but they also document the long post-service history of an exceptionally early form of British chemical-warfare protection.