gas

「ハート徳島」は2006年にSusan Mercerさんが設立した動物福祉団体。The Japan Timesにあった記事からの引用です。
動詞のgasは「毒ガスで窒息［中毒］させる」という意味（『プログレッシブ英和中辞典』小学館）。ここでは「ガス室で処分される」と解釈できます。callingと思える仕事に出会えることは幸運なことですし，身を捧げられるのは素晴らしいことですね。（Koyamamoto）

Strays become woman’s calling
Susan Mercer's NPO safe haven in Shikoku
It’s a typical evening in the Mercer-Tojo household. Susan Mercer, 37, has just settled down their 2-year-old for the night, tucking him in as he cuddles with five or six cats. Several dogs prowl restlessly, eager for a pat or a kind word. Scooping a kitten off the floor, Mercer settles down to wait for her husband, Hitoshi Tojo, who has gone to pick up two aging cats whose owner just passed away.
Mercer and her husband run Heart Tokushima, a nonprofit animal rescue and shelter serving Shikoku. But they do more than take care of stray animals. As Mercer explains: “We are helping people, the people who love these animals. Recently, we took in the two senior cats because the (deceased) owner’s elderly sisters had nowhere to keep them. Their only other option would be animal control, where the cats would be gassed. The family was so grateful for our help during their time of grief.”
http://www.japantimes.co.jp/community/2013/10/11/our-lives/strays-become-womans-calling/#.Ulh1-SjxpQI