In an emergency, inaction or the wrong actions can result in confusion, injuries, and damage.A wide variety of situations, both man-made and natural, could require emergency response in your workplace. For example:

  • Fires
  • Explosions
  • Floods
  • Tornadoes
  • Earthquakes
  • Hurricanes
  • Toxic material releases
  • Radiological and biological accidents
  • Workplace violence
  • Civil disturbances
OSHA says that your workplace emergency action plan must account for different ways to respond to different types of emergencies. For example, in the event of a tornado, you don't want to send employees outside. You want them to seek shelter in a safe place within your facility. On the other hand, in a fire, you want them to be able to flee the building quickly and safely.The type of building you work in may be a factor in your decision. Most buildings are vulnerable to the effects of disasters such as tornadoes, earthquakes, floods, or explosions. The extent of the damage depends on the type of emergency and the building's construction.
Modern factories and office buildings, for example, are framed in steel and may be structurally more sound than small business premises. In a disaster such as a major earthquake or explosion, however, nearly every type of structure will be affected. Some buildings will collapse and others will be left with weakened roofs, walls, or floors.
OSHA advises employers to consider the conditions that would require evacuation and conditions that would indicate the need for alternative action, and plan accordingly. For example, think about what would happen if a part of your facility caught fire? What would happen if there was severe flooding in your immediate area? How would you respond to a chemical spill? What would you do if an ex- employee with a gun was threatening employees?

Shelter-in-Place

"Shelter-in-place" means selecting an interior room or rooms within your facility, normally ones with no or few windows, and taking refuge there. In many cases, local authorities will issue advice to shelter-in-place via TV or radio.
Certain natural disasters such as tornadoes or hurricanes would call for sheltering-in-place. So would chemical or biological releases of such a magnitude outside your facility that going outside would be hazardous.
You should designate safe havens within the facility for employees to shelter-in-place until the danger has passed. You may need several locations to accommodate all employees. Be sure to hold shelter-in-place drills as well as evacuation drills.
Employees Who Remain Behind Certain equipment and processes may need to be shut down in stages or over time. In other instances it is not possible or practical for equipment or process to be shut down. 
If you require any employees to stay behind in an emergency, then your emergency action plan must describe in detail the procedures to be followed by these employees. All employees remaining behind must be capable of recognizing when to abandon the operation or task and evacuate before their evacuation path is blocked.