A safe room is a small hardened room where non-combatants shelter during an attack, with walls of at least 40 cm of earth or the equivalent, a solid door, no windows or only small shuttered ones, ventilation that cannot be blocked from outside, water, a bucket toilet and a prearranged all-clear signal. It is for intrusion only, so keep each room small, give it a second way out for fire, and allow one 10 cm vent for each 9 occupants.
Part of Defensive Architecture
A safe room or refuge point is a designated hardened space in which children, the elderly and the injured shelter for 24-48 hours during a threat, usually inside the strongest building of the settlement.
The Safe Room Works Against Intruders And Fails Against Fire
The defensive-architecture guide asks every settlement for at least one safe room. Its requirements: walls of at least 40 cm earthbag, rammed earth or equivalent (the ballistic caveats are in Ballistic Resistance by Material); a solid hardwood door of 10 cm or more, or a metal-clad door, with a drop bar or several bolts; no windows, or small ones with heavy shutters through which a person cannot enter; ventilation that cannot be blocked from outside, with concealed vents offset so that a projectile cannot enter directly; water, a bucket toilet with cover material, and a way to signal the all-clear from outside, such as a prearranged knock or code. It places the room ideally in the gathering hall, or as a reinforced room in each housing cluster, and expects it to sustain people for 24-48 hours.
The household guide states the matching rule: build the safe room for the intrusion case only; for fire it is the wrong place, so leave the building and do not shelter in a closed room from a house fire (Inner Hardened Zone). A barred door is the one place the exit rule appears to be broken on purpose, and the way to reconcile the two is size: a bar can be lifted by the few people inside, on a room that cannot hold a crowd.
Worked Example: Air In A Closed Room
Inputs (standard physiology and workplace figures, recalled and not read from this corpus): carbon dioxide output 0.2 L/min per person at rest; outdoor air 0.04% carbon dioxide; a design limit of 0.5% (5,000 ppm), the 8-hour workplace limit as I recall it. Floor space 2 m² per person (Emergency Shelter Capability) and a ceiling 2.5 m high (assumed), so 5 m³ of air per person. The vent figure is the corpus’s: a 10 cm pipe 3 m tall moves about 6.6 L/s when the room is 10 K warmer than outside (Ventilation and Odor Control), and a 2 m/s wind can overrule it.
- Sealed room, time to 0.5%: carbon dioxide allowed per person = 5,000 L × (0.005 − 0.0004) = 23 L; at 0.2 L/min that is 23 ÷ 0.2 = 115 minutes, about 2 hours.
- Fresh air needed to hold 0.5% indefinitely: 0.2 L/min ÷ (0.005 − 0.0004) = 43.5 L/min = 0.73 L/s per person.
- One 10 cm vent at 6.6 L/s serves 6.6 ÷ 0.73 = 9 people. Two serve 18.
- People also give off about 100 W each at rest (Emergency Shelter Capability), so 9 people are 900 W; the room warms, and the stack flow rises with it, while in hot weather the room can become unbearable with a small vent.
So a closed safe room with no ventilation is unsafe after about two hours, well short of the 24-48 hours the guide wants, and the vents are part of the life-safety design, not a detail.
What You Need
- Thick walls and a solid door, barred by a bar one person can lift
- A second way out: a hatch, a breakaway panel or a door onto a different corridor, which opens to leave, never to let anyone in
- Vents: one 10 cm pipe per 9 occupants, offset and screened
- Water and food (Supplies & Duration Planning)
- No stove, no open flame; a lamp only on a fireproof surface and only in a vented room
- A signal code for the all-clear, rehearsed
Method: Plan The Room
Step 1: Decide who it is for and count them. Size the room for them and no more: 2 m² each is the emergency-shelter guide’s figure.
Step 2: Put it inside the hardest building and away from the likely fire sources (Location & Access Design).
Step 3: Build the walls and door, and the second way out.
Step 4: Fit the vents, offset so nothing can be dropped through them.
Step 5: Stock it, and rehearse going in, barring the door, signalling and coming out, in the dark, with the children.
Step 6: Teach the fire rule: if there is smoke or fire, leave by the second way out and do not stay.
Common Mistakes
- One large refuge for the whole settlement. A bar cannot be lifted against a crowd.
- A refuge with one door and no vent. Air runs out in about 2 hours, and fire has no way out.
- A lamp or stove in the refuge. It burns the air and makes carbon monoxide.
- Never rehearsing. People forget the signal and the bar under stress.
Safety
A barred room is a trap in a fire
Any room holding more than a handful of people exits outward by pushing, with nothing to work first. The safe room is the exception only because it is small, because its bar can be lifted by the few inside, and because it has a second way out. Never light a stove or burn fuel in it, keep it vented, and leave at once if there is smoke.
What’s Next
- Learn next: Location & Access Design — where to put it
- Combine with: Supplies & Duration Planning — what it must hold