The M.42 filter was the successor to the T.35 filter, made to improve the filtering capabilities against hydrogen arsenide and hydrogen cyanide.
History[]
Soon after Italy entered the war, the army realized that the allies might decide to use hydrogen arsenide and hydrogen cyanide, substances that were not filtered efficiently enough by the current Italian filters, and therefore a batch of German-made SCM-41 was purchased, with plans to get more. Nearing the end of 1942, a new and improved filter was put into production, the M.42. Although those were available by the beginning of 1943, they didn't see widespread use.
Overview[]
Insides of the M.42 filter
The M.42 filter was painted dark brown and contained the following filtering layers, from top to bottom:
- A particulate filtering layer
- An activated charcoal layer
- A smoke and arsine filtering layer
The charcoal was treated with the same materials used to treat the soda-lime layer on T.35 filters, but with the addition of a solution that contained silver and copper salts, useful at combating hydrogen arsenide and hydrogen cyanide, something the T.35 filter couldn't do as efficiently.
Before being opened, the bottom is covered by a rubber seal and the top is closed using a 40mm cap. After the filter has been opened for the first time, it could be closed again using the 40mm lid and the same rubber seal, which is attached through a string to the cap.
Markings[]
The M.42 filter has three main markings:
- A the bottom of the filter there is the date of production.
- The two symbols on the top near the filter thread are the manufacturer's logos.
- Near the manufacturer's logos, there is the name of the filter, M.42.