Version: UFO AI 2.4-dev IA-32 3 Sep 2011 Win32 DEBUG
I started a campaign and fought against 2 taman + 2 spiders in my first mission. When I returned home, I noticed that I had 4 breathing apparatus available.
It seems an unnoticed bug. According to the blood spider authopsy, "the creature is a complex robot without any organic components". Being fully mechanical, it does not require a Breathing Apparatus to store "a gas mixture compressed into a liquid state" to survive in our "unbreathable atmosphere".