Blasting signals and warnings

Employers must post a code of blasting signals equivalent to Table U-1 in one or more conspicuous places at the operation, and all employees must learn and follow that code. See 1926.909(a).

• Post the code where employees and vehicle operators can readily see it (for example: site office, equipment staging area, and main entrances).
• Require training or briefings so every employee is familiar with the signals and their meanings, and make compliance a condition of work.
• Place danger signs at suitable locations to reinforce the posted code.

The code must include the same three signal types and timings described in Table U-1: a warning signal, a blast signal, and an all-clear signal. See 1926.909(a).

• Warning signal: a 1-minute series of long blasts given 5 minutes prior to the blast.
• Blast signal: a series of short blasts given 1 minute prior to the shot.
• All-clear signal: a prolonged blast given after the blast area has been inspected.

If you use an alternate set of signals, they must be clearly equivalent so workers understand the timing and meaning.

The blasting signal code must be posted in one or more conspicuous places at the operation and danger signs must be placed at suitable locations. See 1926.909(a).

• Conspicuous places include site entrances, the blaster’s office or control point, crew staging areas, and locations where vehicles and equipment are marshaled.
• Danger signs should be placed at access points, pedestrian routes, and along public rights-of-way that enter the danger zone so passersby are warned.
• Make sure postings are durable, legible, and located where workers and the public can see them before entering the blasting area.

The blaster in charge must give the loud warning signal before a blast, and only after confirming that surplus explosives are secure and that all employees, vehicles, and equipment are at a safe distance or under sufficient cover. See 1926.909(b).

• The blaster in charge is the person responsible for the blasting operation and for determining when it is safe to give the warning.
• The warning signal must precede the blast according to the posted code (for example, Table U-1 timings).

The blaster must make sure that all surplus explosives are placed in a safe location and that all employees, vehicles, and equipment are at a safe distance or under sufficient cover before giving the warning signal. See 1926.909(b).

• Secure or remove any unused or excess explosives from the firing area.
• Verify by observation or communication that workers have cleared the danger zone, equipment is parked safely, and vehicle operators are aware and positioned safely.
• Use cover, barricades, or sheltering as needed when distance alone is not sufficient.

Flagmen must be safely stationed on highways that pass through the danger zone so they can stop traffic during blasting operations. See 1926.909(c).

• Position flagmen at appropriate points to prevent vehicles from entering the blast area while blasts are being prepared and fired.
• Provide flagmen with appropriate high-visibility clothing and communication methods to coordinate with the blaster in charge.
• If flagging alone is insufficient for public safety, use additional measures (temporary road closures, detours, or law enforcement assistance).

It is the duty of the blaster to fix the time of blasting. See 1926.909(d).

• The blaster determines the exact timing after considering safety checks, traffic control, and notifying affected personnel.
• The blaster should coordinate timing with other site operations and with any flagmen or traffic controllers to ensure everyone is clear of the danger zone.

Before firing an underground blast, the blaster must give a warning, carefully guard all possible entries into the blasting area (including any openings about to hole through), and make sure all employees are out of the blast area. See 1926.909(e).

• Guard every tunnel, drift, raise, or access that could let people enter the blast zone, using barricades, attendants, or locked/monitored doors.
• Pay special attention to openings that are about to break through into another working area; those entrances must be carefully guarded until the blast is complete and the area is inspected.
• Only after a careful inspection confirming the area is safe may the all-clear signal be given.

Table U-1 specifies that the warning signal is a 1-minute series of long blasts given 5 minutes prior to the blast, and the blast signal is a series of short blasts given 1 minute prior to the shot. See 1926.909(a).

• Warning signal: 1-minute series of long blasts, starting 5 minutes before the blast signal.
• Blast signal: series of short blasts, given 1 minute before the actual shot.
• After firing and inspecting the area, the all-clear is given by a prolonged blast.

Yes, employers may use alternate signals so long as the alternative is clearly equivalent to Table U-1 and employees are trained to recognize and respond to them. See 1926.909(a).

• "Equivalent" means the alternate system provides the same pre-blast timing, distinct signal types, and unambiguous meaning for warning, blast, and all-clear.
• Document the alternate system, post it conspicuously where the Table U-1 code would be posted, and train all employees to ensure they understand and conform to it.
• When visibility or audibility is limited (e.g., in noisy or enclosed areas), use combinations of audible, visual, and verbal communication to ensure everyone is warned.

No; a simple verbal announcement by itself does not satisfy the requirement unless it is part of a code that is equivalent to Table U-1 and posted for employees to follow. See 1926.909(a).

• The standard requires a posted code equivalent to Table U-1; the Table specifies distinct audible signals with specific timings.
• If you rely on verbal announcements, they must be incorporated into a clear, posted code that provides the same advance notice and unambiguous meaning as the Table U-1 signals.
• Train all employees so they do not rely solely on ad hoc verbal warnings during operations.

Employers must place danger signs at locations that alert employees and the public to the blasting hazard and prevent inadvertent entry into the danger zone. See 1926.909(a).

• Place signs at site boundaries, access points, pedestrian routes, and any public rights-of-way that intersect the blasting area.
• Make signs clear, durable, and visible from expected lines of approach; include instructions or directional warnings if needed.
• Combine signs with flags, barriers, or attendants for added protection where signs alone may not prevent entry.

All employees at the operation must be required to familiarize themselves with the posted blasting signal code and conform to it. See 1926.909(a).

• Training or briefings should cover the meaning and timings of the warning, blast, and all-clear signals, and what each worker must do when they hear them.
• Include new-hire orientation, pre-shift briefings, and refresher training when procedures or site conditions change.
• Keep a record of employee training and verbal acknowledgements as a best practice to show compliance.

The all-clear signal is a prolonged blast given after the inspection of the blast area and it indicates it is safe to re-enter the blast area. See 1926.909(a).

• The blaster or another authorized person must inspect the blast area for unexploded materials, damage, or hazards before giving the all-clear.
• Do not allow workers, vehicles, or equipment to re-enter until the prolonged all-clear signal has been given and the blaster confirms safety.

If flagmen cannot safely stop traffic passing through the danger zone, the employer must take additional measures (such as delaying blasting, rerouting traffic, or using temporary closures) to ensure public and worker safety; flagging alone is the baseline requirement. See 1926.909(c).

• Consider coordinating with local authorities for temporary road closures or detours if traffic cannot be reliably controlled by flagmen.
• Post extra warning signs, use barricades, and station additional attendants to keep vehicles clear of the blast area.
• Never proceed with blasting until the blaster in charge is satisfied that traffic is controlled and the area is safe.

Per Table U-1, workers should receive a warning signal (1-minute series of long blasts) starting 5 minutes before the blast, and a blast signal (series of short blasts) 1 minute before the shot. See 1926.909(a).

• The 5-minute warning gives workers time to stop tasks and move to a safe distance or cover; the 1-minute blast signal is the final alert prior to firing.
• Employers using an equivalent code must provide the same clear and practicable advance notice.

All surplus explosives must be placed in a safe location before the blaster gives the warning signal. See 1926.909(b).

• Remove, secure, or otherwise render inert any explosives not needed for the immediate shot so they will not be disturbed by the blast or present an additional hazard.
• Document procedures for handling surplus explosives and train personnel responsible for securing them.
• If surplus explosives cannot be moved, provide additional protective measures (distance, barricades, or evacuation) before proceeding.

The blaster must carefully guard any entrances to working places where a drift, raise, or other opening is about to hole through, give warning before firing an underground blast, and make sure all employees are out of the blast area. See 1926.909(e).

• Guard potential breakthrough points with barricades, attendants, or locked doors to prevent accidental entry.
• Communicate the hazard and the blasting schedule clearly to crews on both sides of the potential breakthrough.
• Inspect both sides after the blast and before allowing re-entry, and only give the all-clear after a satisfactory inspection.

Yes, the blaster has the duty to fix the time of blasting and must not give the warning or fire the blast until all required safety checks (secure surplus explosives; personnel, vehicles, and equipment clear or under cover) are complete. See 1926.909(d) and 1926.909(b).

• The blaster is the on-site authority for timing and safe execution of blasts and must delay if conditions are unsafe.
• The blaster should communicate delays to crews and traffic controllers and re-issue the posted warning sequence when ready.

While 1926.909(a) requires employees to familiarize themselves with the code, employers should document that training or briefings occurred using attendance records, signed acknowledgements, or toolbox talk logs to show compliance. See 1926.909(a).

• Keep a simple training record showing date, content covered (warning/blast/all-clear signals), trainer, and attendees.
• Use pre-shift briefings and have crew leads confirm workers understand the signals before beginning activities near a blast area.
• Although the standard does not mandate a particular form of documentation, records are a practical way to demonstrate that employees were instructed and required to conform to the posted code.