Sounds like you are having a panic attack. The youtuber Cody'sLab accidentally took a wiff of pure, undiluted chlorine, and he is still fine. The MSDS of DCM says that an amount like that should have only caused respiratory tract irritation. However, DCM is a known carcinogen, so it's best to not breathe in the vapors. May I ask if that room had any ventilation such as an industrial fan? Again, I'm just a random person on the internet, if you are really worried you should ask a doctor.