Choosing safe refuge areas
When choosing a safe refuge area, do not assume a guarantee of safety; however, understand that the safe refuge area is possibly the safest areas available for building occupants.
Most buildings (unless designed as shelters) will sustain catastrophic damage if they take a direct hit from a violent EF4 or EF5 tornado, since they might not have been designed to withstand the extreme wind speeds that usually occur during these rare events.
Many buildings contain a small interior area, or areas that could serve as the best available refuge area, or parts or all of the building could possibly be converted or reinforced for safe refuge area use.
Selecting the best available safe refuge area involves these main steps:
1. Determine how much space is required to house building occupants
- FEMA recommends the following space guidelines
- Occupants, standing and seated: 5 square feet per person
- Wheelchair users: 10 square feet per person
- Bedridden children or adults: 30 square feet per person
- Sometimes the size of the best available safe refuge area may be less than the recommended guidelines. In this situation, housing more people in less space is preferable to locating them in more vulnerable areas.
2. Review/inspect the building to identify the strongest portion(s) of the building
- This may require consultation with qualified structural engineers or architects as a visual inspection of structure walls will not reveal if or how they are reinforced.
- Keep in mind:
- The lowest level of the building is usually the safest, and below ground space is almost always the safest for a refuge area.
- Minimal or no glass in area (windows)
- Short span roofs are more likely to remain intact (approximately 25 feet or less is best)
- Avoid these:
- Long span roofs (e.g. gyms, auditoriums etc), they are more susceptible to uplift.
- Lightweight roofs (e.g. steel desk, gypsum, wood plank, plywood etc)
- Heavier roofs (e.g. precast concrete planks, channels, tees etc.)
- Windows (extreme winds and debris thrown can break or pop out windows. Windows at the end of corridors can be blown down the corridor)
- Unprotected corridors can turn into wind tunnels if facing oncoming winds. Try baffling these entrances with a solid, massive wall.
- Keep in mind: masonry walls without vertical reinforcements are potentially hazardous, along with load bearing walls.
3. Assess the site to identify other hazards such as large trees, poles, towers etc that may fall, and other objects that could be considered ‘windborne missiles’ and project into the building, or cause secondary incidents (e.g. propane tanks or large vehicles as trucks or buses).
For Mid-Rise and High Rise buildings, the best available refuge areas in these buildings are in the lower floors (basement if available) and in the central part of the building. Stairwells (particularly those with reinforced concrete walls) typically provide the best available refuge. If the stairwells have inadequate capacity for the occupant load, restrooms typically provide the next best available refuge areas.
In large stores and movie theaters, the best available refuge areas will typically be restrooms, closets, or narrow storage areas.
In grocery stores, if restrooms, closets, or narrow storage areas are not accessible, building occupants should crouch in narrow frozen food aisles between freezer cases and cover their heads. The aisles used should be as far away as possible from exterior glass and masonry walls. This should offer protection from a falling roof. Aisles with very tall storage racks should be avoided.
In short, long central corridors often qualify as the best available refuge areas in a school building or similar. In addition to having short roof spans, minimal glass area, and interior locations, corridors usually are long enough to provide the required amount of refuge area space and can be quickly reached by building occupants. Other potential refuge areas include small interior storage rooms, rest-rooms, and offices.