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The Szénmonoxid (carbon monoxide) filter canister is Hungarian-made 40mm (GOST thread) CO filter issued for military, civil defence and industrial purposes. Introduced during the 1950s and 1960s.
The filter come in a dark-olive coloured flat box aluminium alloy canister with a black line on the middle marking that this is a CO filter. A dark-olive coloured cap and a rubber cap on the bottom female thread seals the canister, to the bottom a normal 50M or 60M filter can connect. Protection time was 2 hours and the filter was good for 5 years after manufacturing. Production stopped in 1970 when the new 70M mask and 70M filter came in and it was replace by the Soviet DP-1 filter, but it remained in service till the early 1970s.
The CO was oxidised by Hopcalite I (50% MnO, 30% CuO, 15% Co2O3, and 5% Ag2O) to form CO2 which is not poisonous. A dryer layer is necessary because hopcalite looses its filtering capacity when contacting humidity or water. The dryer is calcium chloride or activated charcoal as in normal NBC filters, both suits well for this work.
A big “CO” sign and a black line around the body marks this filter as a CO filter. On the other side a short sign tell that the protection time is 2 hours. The manufacturing date can be embossed as on the 50M and 60M filters or painted on a smaller white area on the black line.
- Légoltalmi radiológiai-biológiai-vegyvédelmi alapismeretek (book-1962)