I rely on Asimov and the gas companies. If you think what I say is wrong, take it up with the utilities; I know the science author is no longer with us.
I am not questioning your statement about a safeguard against an explosion or other disaster, however.
Mercaptan is made of carbon, hydrogen and sulfur so it just burns off. It’s added to natural gas in a very minute amount because it is so pungent. It’s actually what is smelled due to flatulence.
I’m not sure what Isaac Asimov has to do with this but I’ll restate what I’ve said before.
A properly adjusted burner with adequate oxygen will likely not create carbon monoxide. When that oxygen is reduced (due to a sealed room for example), at some point there is not enough oxygen to continue creating carbon dioxide and instead carbon MONOXIDE is created.
That is: one oxygen molecule instead of two bonding with the carbon molecule.
I’m a retired HVAC tech with almost 40 years experience. I’m done with this conversation but I think you should convince your mother not to use the stove for heat unless it’s an emergency.
I am not trying to be argumentative. I have the best intentions in what I say and I assure you I mean only to be positive. 
I quote from Asimov’s Building Blocks of the Universe, 1974 edition (pp. 107-08):
“Hydrogen sulfide [which is given off by rotten eggs!] is quite poisonous, even more so than carbon monoxide. It is not as dangerous as carbon monoxide, however, because of its odor. By the time there’s enough of it in the air to do considerable harm, the odor is unendurable. People open the windows or leave altogether. Hydrogen sulfide, in fact, is sometimes deliberately added to cooking gas. When this is done, a gas leak can be smelled at once, and there is less chance that the odorless carbon monoxide will sneak up on you. Mercaptans [the source of a skunk’s smell] are sometimes added and then the odor from a leak is even more noticeable.”
(bracketing mine)
Certainly even the odor of hydrogen sulfide would drive people to safety long before the presence of leaking gas could trigger an explosion. Thankfully.
I think Asimov is wrong on this. CO would be from incomplete combustion, not present in the gas itself.
Ask Southern California Gas.
Are you talking about the Porter Ranch leak? Where do you see that it is leaking CO?
Heck no! I live maybe 45 miles from there! I don’t even know what kind of gas is leaking there.
My post is my cite, but you can Google “producer gas” and “water gas” easily for yourself. Before natural gas was widely used, gas made from coal was the standard, including gasification of coke. In the UK there was a big shift circa 1970 as “North Sea Gas” came online. Burners had to be converted to use the new fuel.
I don’t know when Asimov was writing, but from context, it must have been before natural gas was widely used. Note that natural gas has to be piped from the source to the home – whereas coal gas can be made from coal that has been shipped by road, rail or sea from the mine to your local gas works.
People have a hard time in assessing risk. Too often, people assume that ideal circumstances magically persist. E.g., a perfectly working gas range won’t produce worrisome CO.
Accidents often happen from a series of things that individually usually aren’t all that bad. Discounting each one isn’t the same as discounting the overall risk.
So your range isn’t doing a perfect burn, the house is tightly sealed because it’s cold and you go to bed with the range on. Sometimes this is fatal. How can you be sure it isn’t in your case? Don’t use the range for heat! Simple solution.
The original edition of Asimov’s book was about 1957, by which time natural gas was already in wide use.
And FYI, neither of us is foolish enough to go to bed and leave the stove top unattended with burners burning. :rolleyes:
That system would never get past safety regs in Europe. Many years ago, appliances like boilers would have a permanently lit pilot light. If the gas gad to be cut off for some reason, the gas supplier would have to visit every house to make sure that pilot light were switched off.
My gas appliances have spark ignition. To light the hob, I have to hold the control down and turn it on, that opens the valve and starts the spark. If I release it too soon, the gas supply is cut off - no pilot. The boiler is fully automatic but works the same way - you can hear the tick tick tick when it cuts in. If my power was cut off, I could light the hob with a match, but the safety still applies - no heat from a flame = no gas to the burner. No power means no gas heating for me.