Shelter in Place During Chemical or Biological Threat

Move to an interior room on the lowest safe level (basements are good). Close all doors and windows. Turn off ventilation systems, air conditioning, and heating. Use heavy plastic sheeting and duct tape to seal windows, door frames, wall gaps, and vents. Cover door handles and seams thoroughly. Overlap plastic 6 inches at joints. Work quickly but ensure complete coverage.

Do not seal yourself in a room with incomplete planning—ensure you have water and can signal for help before sealing exits.

Seal gaps around pipes and electrical outlets. If you have a working HEPA filter or air purifier, place it centrally and run it continuously. Improvised filtration: stack furnace filters, charcoal, and cloth layers in a box with a battery-powered fan blowing through. Crack a window slightly if CO₂ buildup becomes severe (headaches, dizziness) and seal immediately when conditions improve. Monitor occupants for breathing difficulty.

Lack of air exchange can cause CO₂ buildup in 4–6 hours with multiple people. Be prepared to manage this risk.

Shelter in place for the duration of the threat—typically 2–4 hours after the last visible threat (fog, dust cloud, spray) passes. Listen to emergency broadcasts or alerts on battery-powered radio. Stay calm and ration water. Use plastic bags as portable toilets if needed. Account for all occupants. Do not leave until authorities confirm all-clear.

When leaving becomes necessary, plan to move upwind of the contamination zone. Identify the wind direction by watching smoke, dust, or natural indicators. Mentally map your exit route away from the hazard. Wet cloth can provide minimal respiratory protection during brief movement. Gather essential items (ID, medications, water). Do not look back.

Wind direction can shift. If you must leave, move decisively and do not delay.

Remove plastic sealing tape from one window or door corner carefully. Do not disturb sealed dust. Move quickly to higher ground or upwind, away from the visible hazard zone. If outdoors, avoid low-lying areas where heavier-than-air gases concentrate. Get to fresh air as quickly as possible. Maintain distance from other evacuees if possible.

Once in safer air, remove outer clothing and place in a sealed bag. Wash exposed skin with soap and water for 2 minutes. Flush eyes with clean water if irritated. Shower fully if possible. Wash hair last. Discard contaminated clothing safely—do not rewear. If moving to a decontamination station or medical facility, leave bagged clothing outside your vehicle.

Decontamination prevents spread of residual agents. Do this even if you feel unaffected—invisible residues can persist on skin and clothing.