top of page


Constant flow oxygen mask Type N-521.061

Manufactured by Huggenberger, Zurich

The Huggenberger mask is a constant flow oxygen mask which was used by the Swiss Fliegertruppe from WWII until the 1950's.

Wartime examples differ slightly from post-war masks as they were constantly refined and modified according to the aircraft types they were used with.


Constructed around a chamois lined rubber body which is sewn to a metal nose cone, giving the mask its distinctive shape, it is attached to the flying helmet by a three strap arrangement, using large elastic brown fabric straps on both sides and a narrow non-elasticized black fabric front strap on top.

The nose cone features a metal tag with engraved Swiss Flugwaffe equipment (type) number, mask serial number and manufacturer's name.


On order to prevent the mask from freezing, the Type N-521.061 has an integrated heating system with a two-pole plug to be connected to the aircraft’s elecrical system. With postwar masks oxygen from the Agm.39/40 regulator was provided through a narrow orange rubber inhalation tube ("Röhrli") ending into a metal connector. This connector is of the same type like those used for Swiss modified A-13A and MS-22001 masks used with Pilatus P-2 trainers, K+W C-3603/05 fighter bombers/target tugs and Pilatus PC-6 utility planes.

A second, corrugated black rubber hose with a black metal ending acts as an exhalator tube. Possibly this type of hose was chosen to dispose of possible ice buld-up by twisting and squeezing the tube.


The mask offers no provision for an integrated microphone, thus the use of laryngophones for two-way communication was mandatory.

The exact purpose of the two large turning knobs on the front plate is unknown to us. It seems that they  simply serve as attachment screws for the wiring of the heating system.

We hope that our visitors will be able to provide more information. We're also looking for information about the inventor of the mask. It might have been Swiss scientist Dr. Arnold Huggenberger, who patented an oxygen regulator in 1947.

Munerelle Agm.39/40 constant flow oxygen system

manufactured by Huggenberger, Zurich


Differing from the diluter demand system installed in the Swiss Messerschmitt Bf 109E-3 and Morane D-3800 fighters (which used the german Dräger mask and regulator) the Agm.39/40 “Munerelle” is a constant flow oxygen system. During normal operation, this system started to provide oxygen from an altitude of 10’000 feet (3500 metres) and automatically adjusting the oxygen flow with increasing altitude up to 33’000 feet (10’000 meters).

The Huggenberger company in Zurich produced the system, which was based on a French design, for the Swiss Fliegertruppe. 

bottom of page