A cylinder labelled toxic gas (2.3) is hissing in a closed bay. Which preventive and protective approach is correct for that hazard type?

1. Stand downwind in the vapour to identify the smell, then light a match to test flammability
2. Evacuate, keep people upwind, do not enter the cloud, use any required emergency escape mask, and call the emergency services as the written instructions require
3. Open all other Class 3 packages to dilute the gas
4. Hose the cylinder continuously regardless of the written instructions