Bomb threats: emergency evacuation, standoff distances, and reporting procedures¶

Bomb threats demand immediate, disciplined action. Whether delivered by telephone, digital message, or discovered as a suspicious unattended item, every threat must be treated as an active danger until explosive ordnance disposal technicians and law enforcement declare the scene safe. Panic, haphazard evacuations, and careless communications increase casualties. Following standardized federal protocols protects lives, prevents secondary blast injuries, and assists investigators in neutralizing the threat.

Immediate emergency actions¶

If you receive a bomb threat or discover a suspected explosive device, follow these sequential life-safety priorities:

Telephonic threat response protocol¶

Most bomb threats arrive via commercial telephone lines. The recipient of the call is the single most important intelligence source for responding bomb squads. Your objective is keeping the caller talking while recording every possible detail.

Critical questions to ask the caller¶

Ask the following questions calmly and repeatedly. Write down the answers word for word:

1. When is the bomb going to explode?
2. Where is the bomb located right now?
3. What building, floor, room, or outdoor area is it in?
4. What does the bomb look like?
5. What kind of bomb is it?
6. What will cause the bomb to explode?
7. Did you place the bomb yourself?
8. Why did you place the bomb?
9. What is your name and organization?
10. Where are you calling from right now?

Caller voice analysis¶

Carefully listen to and categorize the caller voice characteristics:

• Tone and Temperament: Calm, excited, angry, hysterical, fearful, laughing, crying, intoxicated, or clinically detached.
• Vocal Quality: Loud, soft, raspy, deep, high pitched, clear, muffled, cracking, whispering, or robotic synthetic text-to-speech.
• Speech Mechanics: Rapid, slow, slurred, stuttering, lisping, nasal, disjointed, reading from a prepared script, or foreign language syntax.
• Accents: Regional domestic accents, international accents, or deliberate phonetic disguise.
• Familiarity: Did the voice sound familiar to you or remind you of any former employee, tenant, student, or client?

Auditory environment and background sounds¶

Listen closely to the background environment behind the speaker voice:

• Street and Transit: Heavy automotive traffic, sirens, train horns, railway track clatter, subway rumble, bus air brakes, or airport jet engines.
• Workplace and Industrial: Factory machinery hum, hydraulic presses, pneumatic tools, kitchen clatter, typing keyboards, office chatter, or cash registers.
• Domestic and Social: Children crying, television or radio broadcasts, barking dogs, loud party music, restaurant bar glass clinking, or outdoor wind gusts.
• Telecommunication Characteristics: Cellular line static, audio dropout, digital compression, public payphone coins, VoIP echo, or PA system announcements.

Line preservation procedure¶

When the caller terminates the call, do not hang up the handset. Place the handset down on the desk with the line active. In many modern enterprise phone systems and telecommunications networks, keeping the connection open preserves the switchboard trace, session logs, and automatic number identification (ANI) data. Immediately use an alternate landline phone or walk to another office to call 911 or your local emergency dispatch center.

Written, digital, and email threat procedures¶

Bomb threats delivered through written documents, email, web forms, or social media platforms require strict physical and digital evidence preservation.

Physical letters and handwritten notes¶

If a handwritten or typed threat letter is discovered:

• Immediately cease handling the paper. Do not pass it around to colleagues or supervisors.
• Place the document inside a clean plastic document protector, zip-top bag, or paper folder. Handle only the outer edges or corners to preserve latent fingerprints, DNA, and chemical explosive traces.
• Preserve any mailing envelope, postal stamps, package wrapping, twine, and tape.
• Secure the room or area where the document was discovered until forensic detectives arrive.

Digital messages and emails¶

If a threat is received via corporate email, direct message, or online form:

• Do not delete, reply to, or forward the email message internally. Forwarding emails can strip original SMTP transmission headers.
• Take high-resolution full-screen captures showing the message body, sender address, subject line, and accurate system clock timestamp.
• Extract and save the raw full email message headers (RFC 822 format), which contain originating IP addresses, mail transfer agent hops, and authentication DKIM/SPF signatures.
• Contact your internal cybersecurity or IT infrastructure team immediately to freeze mail server logs, firewall connection tables, and proxy records.

Bomb threat standoff distances¶

Explosive devices generate lethal shockwaves, intense thermal radiation, and high-velocity shrapnel. Fragment distribution extends far beyond the structural collapse zone. The following table outlines standard explosive threat categories, minimum building evacuation distances, and mandatory outdoor fragmentation danger zones established by federal counterterrorism agencies:

Always treat the outer perimeter of the outdoor fragmentation danger zone as the safe staging line for all unshielded personnel.

Radio frequency hazard and electronic communications¶

Modern explosive ordnance disposal teams enforce strict radio silence protocols around suspected devices. Many improvised explosive devices (IEDs) utilize commercial electro-explosive devices (EEDs), electric matches, or blasting caps that are vulnerable to accidental detonation by electromagnetic fields.

Electromagnetic induction hazards¶

Transmitting radios, cellular phones, walkie-talkies, and mobile data terminals emit radio frequency (RF) energy. If an unshielded antenna transmits near the firing circuit or leg wires of an electric detonator, the wires act as receiving aerials. The induced electrical current can match or exceed the minimum firing energy of the cap, triggering premature explosion.

Radio transmission safety distances¶

Adhere to the following minimum standoff distances when operating electronic transmitters:

• Handheld Cellular Phones and Smartwatches: Do not transmit within 8 meters (25 feet) of a suspected package or device.
• Handheld Two-Way Radios (1 to 5 Watts): Maintain a minimum transmission standoff distance of 15 meters (50 feet).
• Vehicle-Mounted Radios (25 to 50 Watts): Maintain a minimum transmission standoff distance of 30 meters (100 feet).
• High-Power Emergency Service Base Repeaters (100+ Watts): Maintain a minimum transmission standoff distance of 100 meters (300 feet).

Emergency communications within the danger zone must be conducted verbally or via hardwired landline intercoms.

Evacuation decision making and building clearance¶

The decision to evacuate a facility rests with the designated incident commander, building owner, or executive leadership, in direct consultation with emergency services.

Why you should not pull the fire alarm¶

Never pull the fire alarm system during a bomb threat unless an active, uncontrolled fire is visible. Pulling the fire alarm creates significant hazards:

• Predictable Funneling: Fire alarms cause occupants to rush simultaneously into stairwells, lobbies, and exterior doorways. If perpetrators have placed secondary anti-personnel devices at common egress points, casualty rates rise drastically.
• Loss of Voice Authority: Loud, blaring fire horns and strobe lights eliminate the ability of building managers and police to give audible, adaptive public address instructions directing occupants away from specific threatened zones.
• First Responder Misdirection: Automatic fire alarms summon structural fire apparatus rather than explosive ordnance units, creating street congestion and delaying tactical deployment.

Evacuations during bomb threats should be initiated through calm public address announcements, floor-by-floor runner notifications, or administrative text broadcast systems.

Interior door and window management¶

During an orderly evacuation:

• Leave Doors Open: Leave all interior office, classroom, and corridor doors wide open as you exit. Open doors reduce overpressure shockwave damage by allowing explosive gases to expand freely rather than blowing out walls and doorframes. Open doors also allow police sweeps to visually clear rooms rapidly without forcing locked entryways.
• Leave Windows in Current State: Do not waste precious seconds opening or closing exterior windows. Keep building occupants clear of large exterior curtain walls and glass atriums. Secondary injuries from flying glass fragments represent over 70 percent of all urban blast trauma.
• Grab Immediate Belongings Only: Take coats, purses, wallets, and keys that are immediately beside you. Leaving unattended bags behind creates dozens of potential false-positive suspicious items that bomb technicians must painstakingly clear. Never delay personal evacuation to gather equipment, documents, or personal computers.

Workplace visual search protocols¶

In commercial, educational, and institutional environments, the people most qualified to spot an unusual object are the people who work in that specific room every day. Bomb squad technicians do not know where cleaning supplies belong, which backpacks are normal, or what floor tiles are loose.

If emergency protocols call for a rapid visual sweep before or during an orderly departure, adhere strictly to the two-person quadrant search methodology:

[Ceiling & Light Fixtures (Top Level)]
         ^
         |
[Eye Level to Tops of Shelves & Cabinets (Level 3)]
         ^
         |
[Waist Level to Eye Level: Desks, Chairs, Files (Level 2)]
         ^
         |
[Floor to Waist Level: Carpets, Baseboards, Trash Cans (Level 1)]

Visual sweep rules¶

1. Work in teams of two, searching opposite halves of the room systematically.
2. First search Level 1 (floor to waist height), checking under desks, behind wastebaskets, and under chairs.
3. Second search Level 2 (waist to eye level), checking open drawers, shelves, and countertops.
4. Third search Level 3 (eye level to ceiling), checking top cabinets, wall hangings, and high storage.
5. Fourth search Level 4 (ceiling plenum and lighting), looking for displaced acoustic ceiling tiles, hanging wires, or objects tucked above drop ceilings.
6. Never touch, move, jar, or cover any suspicious object. If an unfamiliar item is discovered, halt the search, mark the doorway clearly, evacuate the immediate area, and report the exact location to incident command.

Secondary device awareness¶

Secondary explosive devices are designed specifically to target first responders, evacuating crowds, and command staff. History demonstrates that secondary devices are frequently positioned where people naturally congregate following an initial alarm.

High-risk secondary locations¶

When evacuating and establishing assembly points, actively avoid:

• Outdoor Waste Receptacles: Concrete, metal, or plastic trash cans positioned immediately beside building exit doors.
• Exterior Planters and Benches: Decorative brick or concrete landscaping fixtures directly outside main entrances.
• Mail Collection Boxes: Freestanding postal boxes located along pedestrian sidewalks.
• Parked Vehicles Near Exits: Unattended delivery vans, rental trucks, or passenger cars parked in emergency loading lanes.
• Evacuation Assembly Areas: Pre-designated rally points in parking lots or courtyards that are publicly advertised on emergency evacuation maps.

If an assembly point feels vulnerable or is located within line of sight of exterior trash bins and parked vehicles, move your group further away to a secondary, sheltered location behind substantial concrete barriers.

Law enforcement and EOD handover¶

When police officers and explosive ordnance disposal (EOD) technicians arrive on scene, their first priority is establishing command and gathering intelligence. The person who received the threat or discovered the item must remain available at the incident command post.

Information checklist for emergency responders¶

Prepare to deliver the following information immediately to arriving supervisors:

• Completed telephonic threat checklist or physical copy of written message.
• Exact time the threat was received and the call duration.
• Exact wording of the threat, including specific locations, device types, and detonation timelines mentioned.
• Accurate headcounts and evacuation status of all building floors.
• Verified locations of any mobility-impaired individuals awaiting assistance in designated areas of rescue assistance.
• Detailed floor plans, master mechanical keys, electronic access control badges, and security camera monitor feeds.
• Details regarding any ongoing construction, scheduled maintenance, or unusual deliveries observed that day.

Related emergency guides¶

• Suspicious package response
• Active attacker and workplace violence
• Civil unrest and protest safety
• Emergency numbers and international dispatch