Blue Russian filter, 1992. I am not entirely sure what these protected against (various nitrogen oxides?), the intake is sealed with a metal cap rather than a regular rubber plug. : r/gasmasks
Respiratory protective filters: colour code, class, etc. | Be Atex
SCOTT Pro2000 CF32 ABEK2P3 Filter - Durasafe Shop
ABEK filters explained - YouTube
How do you choose the right spray mask and filter? | Royal Brinkman
ABEK gas filters: what you need to know
Best gas masks and respirators for survival – The Prepared
sch_tec_FRONT_322 ABEK1P3 eng.ai
MIRA Safety DotPro 320 40mm Gas Mask Filter » Active Violence Solutions (AVS)
ABEK gas filters: what you need to know
Respirator Filters – how to select the correct filter type | Draeger
Respirator Filters – how to select the correct filter type | Draeger
Respirator Filters – how to select the correct filter type | Draeger
Choosing the right filters for your respirator - YouTube