It looks like inhaling detergent fumes
could be fatal, but tbh it seems like it would, at this stage, be a weak plan based mainly on guesswork, as it is not a widespread method, there are very few if any cases of deliberate poisoning.
However, I'll share what I did find:
Detergent poisoning can cause symptoms in many parts of the body.
BLOOD
- Severe change in acid level of blood (pH balance), which leads to damage in all of the body organs
HEART AND CIRCULATION SYSTEM
LUNGS AND AIRWAYS
- Breathing difficulty (from breathing in the detergent)
- Throat swelling (may also cause breathing difficulty)