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The filters of the 33M, 34M, and Népgázálarc were not the same for appearance but structurally all contained the same substances (with a little exception).
External
All of the filters has 40mm thread and a sticker covers the intake which had to be torn of before use.
33M
This was the first filter that was designed in Hungary. The filter is green painted cylindrical canister filter. This is the most spherical.
34M
The firsf filter designed for military purposes in Hungary. The filter is green painted cylindrical canister filter. The shape is very similar to the 70M filter. This filter was in service with the 34M and Gumi munkagázálarc masks with minor modification till the 1960s.
36M
The smallest and lightest filter among this three. It is a green painted cylindrical canister filter.
Substances
The first layer is duck feathers. It is better as smoke filter than compressed cotton because it requires smaller place. The second layer is the activated charcoal which is made of carbonized seeds of stone fruits made by IPTER Műszéntermelő Vállalat. The third layer is diatomite, unlike the activated charcoal which binds physically it binds chemically.
The little exception
The 34M filter was redeveloped in 1941 because during the Hungarian invasion of the Soviet Union the troops have found Zinc arsenate (Zn3(AsO4)2) powder in warehouses which is used to produce Arsine (AsH3). Arsine was used as a toxic agent and the filter of the 34M was useless against it. So the army would have been suffered heavy loses in case of a gas attack. The redeveloped filters got a fourth layer which were protected against arsine and the canisters were marked with an “A” on the top of the filter. The fourth layer was sodium hypochlorite ("bleach") in binder to prevent leak. Sodium hypochlorite reacts with arsine and creates mainly harmless chemicals but because arsenic trioxide only sublimates on higher temperatures in the filter it would be ok. (2 AsH3 + 6 NaOCl = As2O3 + 3 H2O + 6 NaCl). This modification was only used on the 34M filter.
References
- Légoltalmi ismeretek a lakóházi (önvédelmi) szervek részére II. kiadás (book-1952)
- Horler Ferenc: A polgári lakosság önvédelme légitámadások ellen (book-1938)
- Légoltalmi ABC (book-1939)
- http://militiahungarorum.roncskutatas.com/1920_e_f_g_4.html