How can they not able to smell anything?!

I was just out for a while and the moment I returned home, I felt something was amissed. I kept smelling gas! I thought it was illusion or what but it isnt! I'm just able to smell it especially when in the kitchen. So I looked wrong and guess what?! The stove's gas switch was on! omg omg omg la!!! No one uses it except my mum and I was out with her in the morning so left all the males at home. And they've been at home for whole day yet unable to detect the smell?! can u believe it? Even when I alarmed them, yet they still can't smell it! This is way too too dangerous alrd la. If I didnt detect it, something cound to happen 1 lor... I'm thinking what will happen if I'm not at home. Such small thing also didn't notice leh, how low guarded are they and how can I not worry abt them right? Wau Lau la! When ever will they be more alert, pay more attention to their surroundings?!
What a stupid family I have and I can't stand it laaaa!!!