After an airplane crash in the fifties where the 100 percent of deaths made no sense, the FAA discovered the actual cause. A small fire had spread smoke into the cabin. The materials burning formed a poisonous gas, even a tiny bit of which caused instant paralysis. Since then, materials used in cars and planes could not be made of substances that, when burned, caused poison gases. A limo fire in California contained those aftermarket upholstery materials and only the driver, in his separate compartment, got out when a dropped cigarette caused a small fire killing the three passengers.
Our homes and businesses contain these common plastics that, when burned, can cause paralysis. That may or may not have been involved here, but it’s something to think about.
I believe the gas you are looking for, beyond carbon monoxide, is hydrogen cyanide. Hydrocarbon fuels such as foams, plastics, synthetic materials give off large amounts of hydrogen cyanide and other toxic gases that can quickly incapacitate (and kill) a person or pet.
This is why modern fires are far more dangerous (and rapid) than fires were decades ago.
The use of smoke detectors still provides an adequate safety margin in most scenarios allowing a person(s) to evacuate (or suppress) when the fire is small. Sadly, in most fatal fires they were not present or operable.