Natural gas is flammable and in the right concentration explosive. If a leak occurs, the university community should take immediate action to protect themselves from injury.

If a gas cylinder or gas piping should begin leaking, or is suspected of leaking, and if in the judgment of the person or persons responsible for such materials it presents any danger to them or other building occupants, the following steps should be taken:

• Immediately notify building occupants to evacuate the area using preplanned evacuation route. 
• Notify ULPD at 502.852.6111. Provide the following information: 
  • Building name and/or number;
  • Floor number;
  • Room number; and
  • Specific type of gas if known.
• Vacate the area and report to the pre-designated safe area.

Make every attempt possible to direct evacuating personnel away from the area. Building occupants are not to return to the building until instructed to do so.

http://louisville.edu/dehs/occup-health-safety/occup-health-safety-files/laboratory-safety-manual/ (PDF)