The text below discusses four gas masks shown in the last photo attached. It is quoted in its entirety and comes from La Grande Guerra web site. The remainder of the photos are of the funnel type Poliavente gas mask with and without its protective cover.

"GAS MASKS: Until after the Battle of Caporetto, when the English box gas mask was adopted, the Italian gas masks evolved from single purpose (monovolente) to multipurpose (polivolente) filter masks. A. The filter for the first model(top left) was made of a thick wad of gauze over 2 layers of thin cloth. At the moment of use it was necessary to activate it by saturating the cloth with a solution of hydrosulfate and carbonate of soda. It was effective only against chlorine gas. Goggles were worn separately. B. Another monovolente mask (top right), called the Ciamician-Pisci type, had a conical shape. It was made of 10 layers of gauze saturated with an alkaline solution of sodium carbonate and potassium carbonate. To keep the alkaline solution from irritating the users lips a strip of flannel protected the mouth. It, too, offered protection only against chlorine. It was a major cause of a disaster at Monte San Michele on the Carso which was abandoned when the Austrians attacked with phosgene gas. C. The first Italian polivolente mask [lower left] was patterned after the French TN model and appeared on the front in April 1916. It protected against both chlorine and phosgene gas and differed from the French model in that it had 64 layers of muslin rather than 38. It came with celluloid lens goggles that could be worn separately for tear gas protection, but which fogged up easily. D. The later polivolente mask [lower right] based on the French model M2 was called the funnel type. It consisted of a filter of 60 layers of gauze that extended over the face and cheeks completely. The goggles were incorporated into the mask and were made of celluloid. The mask was covered by a rectangular, rubberized cloth which gave protection from rain and prevented the evaporation of the reactive chemicals in the layers of gauze. It was kept in a container carried around the neck on which this message was stenciled, "WHO REMOVES HIS MASK DIES." After Caporetto when the inability of these gas masks to protect against the newer gases became disastrously clear, Italian soldiers were equipped with the far superior English gas masks ."