In the demolition industry, being proactive about your crew's safety is a crucial part of ensuring their well-being. Taking steps to secure your site is also key to ensuring the safety of any bystanders or nearby structures that could be harmed by flying projectiles or other hazards.
This article will explore different safety considerations for explosive demolition work, including appropriate protective equipment and other proactive safety measures site managers can take.
Defining Explosive Demolition of Buildings
Often referred to as building implosion, explosive demolition involves strategically placing explosives throughout a building or structure and timing detonations so that the structure will collapse in on itself rather than outwards.
Technically speaking, building implosion is a misnomer — true implosion happens when the difference between a structure's internal pressure and the pressure outside becomes so high that it collapses into itself. Building implosion, on the other hand, uses explosive devices to destroy a structure's support system, causing it to cave under the force of gravity.
While other demolition methods may be more practical for small structures, explosive demolition is much safer and more efficient for larger buildings, especially those in more crowded areas. Because the building collapses inward, it minimizes the risk of damage to its surroundings.
Additionally, explosive demolition significantly reduces the time it takes to demolish a building. By progressively knocking out critical supports throughout the structure, the building loses its ability to withstand the force of gravity. Then, the demolition team detonates the explosives on the lower floors to initiate a controlled collapse. This whole process takes only a few seconds.
Hazards of Demolition Work
Demolition sites share many hazards with construction sites. However, due to the unpredictable nature of demolition work, there is some additional risk involved.
According to the Occupational Safety and Health Administration (OSHA), common demolition hazards include:
- Hazardous substances hidden within structures, such as asbestos, lead or any other chemicals that would require special handling.
- Unauthorized modifications to the structure's original design.
- Construction changes in the structure's design.
- Unknown strength or weakness of aged construction materials.
- Hazards created during the demo process itself, like flying rock or other debris.
The employer must ensure all workers on a demolition site are fully aware of the potential hazards they may encounter during the project. Additionally, it is the employer's responsibility to provide adequate personal protective equipment and training — responding proactively to potential threats is critical.
The Role of Det Cord and Blasting Caps in Building Demolition
Blasting caps and detonation cords are common tools on any demolition site. Depending on your specific application, you can use them together or in conjunction with other explosives like dynamite or TNT.
Blasting Caps
A blasting cap is a thin, tubular metallic shell filled with small yet highly sensitive explosive charges, which are typically either pentaerythritol tetranitrate (PETN) or cyclotrimethylenetrinitramine (RDX). Demolition teams use blasting caps to detonate larger explosive charges.
Several types of blasting caps exist, but electric blasting caps are the most commonly used. Electric blasting caps (EBCs) have two insulated electric wires attached to one end. These leg wires connect via a thin-filament bridgewire and can be inserted directly into an explosive charge or connected to a length of det cord. EBCs are relatively safe to handle and allow greater flexibility in detonation timing than other cap types, making them especially useful for urban areas.
Blasting caps are susceptible to accidental detonation by environmental factors such as excess heat, static electricity or friction, so demo teams must handle these charges with extreme care.
Detonation Cord
Detonation cord, also known as det cord, detacord or primer cord, is a high-speed linear explosive that consists of two parts:
- A highly explosive PETN core
- A reinforced yet flexible plastic coating
Det cord is useful for various applications across many industries, including mining, quarrying and civil engineering. In demolition, det cord primes and detonates other explosive charges. Typically, you initiate det cord using a blasting cap, which triggers a detonating wave that sets off any attached explosives.
It's important to note that det cord is different from a time blasting fuse (TBF), which takes significantly more time to ignite. In contrast, det cord ignites almost instantaneously upon initiation. Mixing the two up can be dangerous, so be sure you and your crew know which is which.
Safety Measures for Demolition Jobs
According to the OSH Act, Public Law 91-596, employers must provide a safe workplace for their team. By planning ahead and making the necessary personal protective equipment available, an employer can significantly reduce the risk of illness or injury during a demolition project.
OSHA recommends the following steps for creating a safe job site:
Plan Ahead
Making preparations in advance ensures a smooth job. First, a competent person must conduct an engineering survey of the site to evaluate the structure's condition and the potential for unplanned collapse. OSHA defines a competent person as someone who is:
- Capable of identifying existing and potential hazards on a site.
- Authorized to take corrective measures to remove these hazards.
Employers should also plan out fire prevention, first aid and evacuation procedures to prepare for an emergency situation. The employer should also assess the health hazards of the site along with employees' health before beginning demolition, as certain chemicals can aggravate chronic physical conditions like asthma.
Provide and Train
Comprehensive employee training is a crucial part of mitigating demolition-related risks. In addition to providing the appropriate PPE, the employer must provide adequate training on how to properly use and store it. Employees must also ensure employees are able to recognize and avoid or remove hazards that arise during the demolition process.
Protective Equipment for Demolition
All explosive work comes with a degree of risk — making the right protective equipment available on your demolition site reduces the risk of injury or illness due to blasting accidents. Some examples of protective equipment for the demolition industry include:
- Blast mats: Flying debris can injure your team, pedestrians or nearby structures. Steel blast mats stop projectiles, preventing them from flying out of your worksite and venting any gases that may be produced by the explosion.
- Personal fall arrest systems (PFAS): Falling from heights is one of the leading causes of death in the construction industry. Providing suitable fall protection systems is a crucial consideration for any demolition project above ground level.
- Respiratory protection: Explosions can release toxic chemicals into the air, which can damage a worker's respiratory system. Respirators protect employees in several ways. Some filter harmful chemicals from the air, keeping them out of workers' lungs. Some respirators also provide their own supply of clean air for the wearer to breathe.
Choose Protective Equipment From TM International, LLC
If you're looking for top-quality commercial blasting mats, TM International, LLC is here to help. As a leading manufacturer of blast mats, we provide safe and affordable protective products for many different businesses, organizations and agencies that deal with explosives.
Reach out to us today to request a free quote or get more information on how our products can keep your workers safe.