The Ultimate Guide for
Blast-Resistant Buildings

HOW DOES A BLAST AFFECT THE HUMAN BODY? 

The effects of a blast event on the human body will depend on several factors, a person’s proximity to the center of the explosion, the terrain and surroundings within the area of the blast, the cause of the explosion (i.e., the type of gas or other material that caused the event), and the intensity and frequency of displacement waves. 

With these factors in mind, it is important to note that the human body can typically survive high blast overpressure. For example, a 5 psi blast overpressure can rupture eardrums, while lung damage can occur at an approximately 15 psi blast. 

One significant factor that must be considered when taking precautions to protect personnel during a blast event is the impact of blunt force trauma to the human body. Injuries like these can occur with overpressure as low at 1-2 psi, when windows may shatter, and debris is thrown. Crush injuries may occur at slightly higher response levels when the building’s structural integrity begins to fail. 

In a blast event, or explosion, the human body might be thrown, large objects might be propelled at a person, and light objects can quickly become speeding projectiles. Fortunately, a blast-resistant building is designed to protect people from the aforementioned injuries.

A blast resistant building that has the right psi ratings for its intended use and location within your facility can not only protect personnel during blast events; it can also save lives and reduce the risk of nonstructural items causing bodily harm in the aftermath of a blast event.

Because there are so many people involved in oil and gas processing, the financial risk of NOT protecting them as they do their work is huge. Understanding the financial impact of a blast with real-world examples is essential. To do this, let’s take a look at the trickle-down continuous financial costs of a blast event.

WHAT IS RESPONSE LEVEL?

Blast response levels are ratings established by the American Society of Civil Engineers (ASCE) to predict the extent of repair resources that would need to be devoted to a building after an explosion. Their descriptions include:

Low response — Localized building and component damage; the building can be used, however, repairs are required to restore the integrity of the structural envelope; and the total cost of repairs is moderate.

Medium response — Widespread building/component damage; the building cannot be used until repaired; and the total cost of repairs is significant.

High response — Building/component has lost structural integrity; a building may collapse due to the environmental conditions, and the total cost of repairs approaches replacement cost of the building.

Substitute the term "damage level" for "response level," and you have an instant picture of what these ratings mean. Given the options of low damage, medium damage, and high damage, you obviously don't want to be working in an area that is highly damaged during a blast event.

WHAT DOES BLAST-PROOF MEAN?

The word “proof” implies that something is impervious. However, there really is no such thing as a blast-proof building. If you exceed the load that a building is designed to resist, there's a strong possibility that it could fail.

The word “resistant” means that the object can resist some type of hazardous penetration. In our case, the hazard is blasts or explosions, but you may also think of objects that are water-resistant, slip-resistant, heat-resistant, or puncture-resistant.

Blast-resistance has a lot of nuance to its meaning because there are many factors at play that determine the amount of damage during an explosion. Let’s look at the factors in play when it comes to how blast-resistant a building is. 

DESIGN AND ANALYSIS OF BLAST-RESISTANT STRUCTURES

We’ll start with structure because the structural engineering of a blast-resistant building is probably the most critical factor in protection. This goes back to those response levels, mentioned earlier in Chapter 3.

Remember High, Medium, or Low Response? All of them are considered blast-resistant, though not all are equal. And none of them would be regarded as “blast-proof.”

Manufacturers of blast-resistant buildings will have different explanations for their design methodology, or why they design to a specific blast response level. Still, it’s important to look at whether they regard structural integrity as a priority, or if they simply meet the minimum requirements to get their building rated.

BUILDING MATERIAL

Hand-in-hand with the structural engineering of a building is the building material itself. Today’s manufacturers of blast-resistant buildings are wise to take lessons from the past. In some of the early blast events that shaped the industry, onsite offices in temporary trailers were completely destroyed, while metal shipping containers inside the blast zone were still standing, their contents intact. Though today’s designs are far more complex and protective, shipping containers became the basis for an idea to create blast-resistant buildings. Extensive engineering helped create a final design that has led the industry in blast resistance. 

Blast-resistant builders employ many different structural designs and materials. There are blast-resistant structures that are permanent brick and mortar buildings; there are temporary blast structures, there are even tents, sometimes called air shields; and there are modular buildings made of hardened metals that are either portable for temporary use or anchored for permanent use. 

Though many materials can be used in the design, none of them are blast-proof, and their levels of blast-resistance vary.

PROXIMITY TO THE BLAST WAVE

The further you are from an explosion, the less of an impact you will feel. Like structure, proximity to the blast also makes a difference in the damage a building will sustain after a blast. The closer to the blast wave, the stronger the building’s blast resistance should be. 

A high response blast-resistant building placed in a hazardous process area would be very dangerous in the event of an explosion, even though it is technically blast-resistant. A low response building in the same area may sustain little to no damage. 

Both buildings may be resistant to damage in an explosion, but are either really blast-proof? Not really. The most we can do is prepare for the dangers that we know are present.

1. STAFF, EQUIPMENT, AND ASSETS ARE PROTECTED DURING A CATASTROPHIC EVENT

Blast-resistant modules, or BRMs, are built to withstand the devastating damage resulting from an explosion. The people, equipment, and assets inside of the buildings will be protected.

The level of damage is all dependent on the blast rating and the building’s proximity to the hazard. If you work in a classified area, in a building with a low to medium response (which, as mentioned earlier, means it would sustain low to medium damage), your chances of survival are much higher than in a soft-sided trailer, which is still used on some worksites.

2. REDUCE LIABILITY, INCREASE PEACE OF MIND

When the risks to human life are decreased, the amount of liability is also reduced. For every significant blast event that has occurred, when there were numerous fatalities or injuries, the investigation to determine cause and fault begins almost immediately.

Including blast-resistant buildings as safe havens or shelters-in-place can give those who work in hazardous areas peace of mind. Should a catastrophic event happen, it can reduce the company’s liability since it took measures to keep its workforce safe.

3. REDUCE TIME LOST TO RETRIEVE TOOLS OR OTHER EQUIPMENT

One benefit of blast-resistant buildings that's often overlooked is the amount of time, and therefore money, that you will save by storing equipment and tools in blast-resistant tool cribs inside the hazardous area.

Some refinery sites are huge. Often, the time required to get into and out of the classified area involves checking in and out and even arranged transportation.

When you store tools and equipment outside of the blast zone in order to keep them safe, employees must make a trip each time a specific piece of equipment must be used or checked out. When you begin to calculate the amount of time spent going back and forth to retrieve tools, you realize the benefit of just keeping those tools closer. Depending on the size of the workforce, the lost time savings could be huge. The amount of time saved over time might even pay for the cost of the blast-resistant building.  

4. REDUCE THE AMOUNT OF TIME EXPOSED TO HAZARDS

It goes hand-in-hand with reducing time and money, that each time a worker must travel across a worksite to retrieve a tool, they are spending time exposed to hazards.

Reducing the amount of travel time reduces the time that the workforce is exposed to risks.

5. FLEXIBILITY AND MODIFICATIONS

Modular buildings are easy to modify. If the process area changes after five years, and your facility siting study now shows that the blast zone has changed, you may need to modify existing buildings in order to provide protection.

If your building is a multi-section, this might be a matter of adding additional sections. Alternatively, you may choose to use the existing building and add more buildings to accommodate your need. Modular buildings can even be stacked to save space.

How long the building will be in use:

The length of time the building will be in use determines if the building is purchased or leased, which probably affects the cost most of all.

The location of the building in proximity to hazards:

A building’s location on the work-site makes a difference because, even on one site, areas have varying levels of PSI during a blast event.

The duration of exposure is also considered, typically expressed in milliseconds. You will find that BRBs come in several “response levels,” as mentioned in chapter 3, or are rated for a specific PSI and duration of exposure.

The type and size of the building and the number of units needed:

Many people think that all blast-resistant buildings are the same, but in actuality, a blast-resistant building can be made to look like and function as almost any type of building. (Labs, control rooms, lockers, restrooms, tool cribs, break rooms, and more.) Components of structure will affect the cost.

Since buildings come in different sizes, the building’s size affects the raw materials and again, the cost. When it comes to size, another factor to consider is how much the building’s width and height drive the cost of transportation.

If a lot of space is required, you can consider using one or more buildings, or creating a multi-section building, where several components are placed together to create a larger area.

The number of external doors, and If the building requires windows:

Every component of a blast-resistant building must be properly vetted. The most vulnerable elements of a blast-resistant structure are the windows and doors. (These elements are not dangerous. They just require careful engineering.)

Each component being vetted also means that each component must be blast-tested. It would make no sense to put windows into a blast-resistant building without knowing if they could withstand a blast. So the windows must be blast tested, and when considering doors, the door itself must be tested, as well as the latches and hardware.

Adding windows to the building means that the studs must be cut to accommodate the windows. Cutting the studs of a blast-resistant building means that there is engineering involved to determine that it retains its structural integrity.

When it comes to windows and doors, we must figure the cost of raw materials, and also the cost of engineering required for the placement, to ensure that the building is safe.

The type of interior components required (plumbing, electrical connections, communications, fixtures) as well as the level of interior finish:

All interior components must be rugged enough so that they don’t become projectiles in a catastrophic event. (Projectiles are the primary source of injury and death during blast events.) This means that all interior components, like electrical connections, plumbing fixtures, cabinetry, furniture, etc. could affect the cost, when compared to those used in buildings where blast-resistance is not a factor.

An electrical finish is also a factor in the cost of a building. Some blast resistant buildings use surface mounted electrical, so all of the conduits is visible on the finished walls. While the look is more industrial, this allows easier access and is less expensive.

On the other hand, if the visual aesthetic of the building is essential, a blast-resistant building can have a more finished look, but it will affect the cost, both upfront and if repairs are needed at any point.

You must also consider if the interior space of the building needs to be ADA compliant. This will mean wider door frames, ramps, possibly lower counters or workspaces, and other considerations for those with disabilities.

Special accessibility for ADA compliance is also taken into consideration when figuring a bid for a blast-resistant building.

1. BLAST-RESISTANT DOORS ARE HEAVY! 

Yes, blast-resistant doors are heavy, some weigh in at 450 pounds or more. It makes sense because they’re blast-resistant and made of heavy steel. The weight means that they have hydraulic mechanisms to make opening and closing them easier and to prevent slamming. 

Because of these factors, blast resistant doors require regular maintenance to avoid sagging and out-of-alignment hinges or latches. Without proper care, the doors may not close properly, which could affect the building’s efficacy in a blast event. And, while it’s not common, a large, heavy door could cause injury if it’s not properly maintained and slams on a hand or foot.

WHAT CAN YOU DO? 

To avoid problems with these doors, it’s important to note that they should never be left open to allow the free flow of traffic. Leaving the door open will allow the blast wave to enter the building in the event of an explosion. 

Regular maintenance will also help prevent problems with blast-resistant doors and could include something as easy as a visual inspection to ensure that all fasteners are tight and that hinges and latches are functioning. We’ll talk about the maintenance of blast resistant doors in more detail in the next section. 

1. SERVICE FOR POOR HVAC/AC PERFORMANCE

Typically, when an HVAC/AC needs service, there is a filter that needs to be changed, and/or the coils need to be cleaned. Occasionally, the technician will also reload coolant or replace a sensor if it’s not functioning. 

At RedGuard, our blast-resistant buildings are designed with specialized HVAC units to provide proper and sufficient heating and air conditioning for that building or unit size. We recommend that they run in an ambient setting of no lower than 73 degrees for cooling and no higher than 78 degrees for heat. 

These units are often placed in locations with extreme temperatures that require the units to run more frequently than other commercial installations. Higher traffic in and out of the building will also cause it to run more frequently and need service more often. 

Due to the environment, usually places with more dust and particulate in the air, the filters should be changed regularly, preferably every thirty days. In hot, dusty climates or where debris is more common, they may need to be replaced even more often.  

2. MAINTENANCE ON BLAST-RESISTANT DOORS

A visual inspection of blast-resistant doors should be done every 60 days, or more often in high traffic areas. The visual inspection will include checking these details:

• Does the door seal correctly or have issues with slamming? Those are signs it needs to be serviced. 
• Are the hinges still aligned properly? Because of its weight, the door may need to be realigned on its hinges or replaced. 
• Do the door handles need to be tightened or replaced? 
• How is the viscosity of the fluids in the door’s hydraulic mechanisms? In areas where temperatures are subject to change, the viscosity of fluids could be affected, causing doors to slam or have difficulty latching. 

If you’ve decided to take on this maintenance yourself, you’ll need to know what to look for and how often. An effective service team will be ready to either guide you through the process or come out to make regular inspections during building maintenance. 

And, while the doors are heavy, it’s important to remember that they are a factor in saving lives. Doors on blast-resistant buildings should never be propped open. The amount of wear and tear on the doors when they weigh 450 to 800 pounds, and the amount of traffic going through the doors in one day are significant factors in these repairs.

MOVING INTO PROJECT MANAGEMENT   

Once a purchase order (PO) is received, the project is handed over to the project management group. At that time, a purchase order review begins to make sure that the company can/will accept the purchase order. 

Not all POs are accepted immediately. Sometimes the blast-resistant building manufacturer requires changes in the contract language, or there could be details to be clarified before the PO is formally accepted. 

Occasionally, some new specs may show up in this stage. For example, the purchasing agent may not have clarified the type of HVAC system required or whether the system should be redundant. Before the PO is accepted, the building vendor will send it back with language defining these types of details, and the customer will need to approve the additional details. 

Depending on the complexity of the changes, and the responsiveness of those involved, getting the PO approved could take between a few days and a few weeks. The project manager will do what they can to ensure the process keeps moving until both parties sign-off on the PO. 

THE KICK-OFF AND DESIGN STAGE MEETINGS

Once the purchase order is formally accepted, the floor plan is emailed to the customer for review, and an initial kick-off meeting is scheduled. 

The kick-off meeting gives the salesperson the opportunity to introduce the customer to the project manager, and for the project manager to begin talking about expectations for the project. During the kick-off meeting, the customer has reviewed the floor plan in advance, allowing for more design conversations to begin. In this meeting, there will also be a detailed review of the architectural, mechanical, electrical, plumbing, structural, and blast components of the building. Additional meetings may be required for each of these components of the blast-resistant building. 

Once the project is under the care of the project manager, the original salesperson will be relatively hands-off unless their assistance is needed. For example, their assistance may be required to discuss change orders or commercial changes, which occur when there are customer-driven changes that result in an increase or decrease to the contract price. 

Depending on the customer’s preferences, calls will be set up weekly, or updates can be given periodically by email. The important part is to keep an open channel for communication flowing.

BLAST-RESISTANT BUILDING TIMELINES

There’s no real way to narrow down how long a blast-resistant building project will take since the timeline will vary based on factors like building size, design complexity, material availability, state-specific approval processes, and project backlog. 

Project sizes can vary from simple single unit buildings, which may be ready in a matter of weeks, to large multi-section complexes which could take months, or the better part of a year. The best way to find out the timeline is to ask about the specific details for your project.

As a general rule, ask questions. How will the project be managed? What happens if we have change orders? Will this change affect my projected delivery date? 

In most cases, project management begins when the order is accepted and ends when it leaves the vendor’s production facility. Once the blast-resistant building is installed, regular maintenance and any issues that come up are handled by a qualified service department. 

CUSTOMER APPROVAL AND FINALIZING DESIGNS

Once the kick-off meeting has occurred, initial introductions have been made, and the customer signs off on the floor plan, then things begin to move forward. It’s important to have an approval process in mind on your end when approval is required at other stages. This will help the process run in a timely manner. 

Other meetings that will need to occur and places where other approvals may come into play will be when discussing the architectural, mechanical, electrical, plumbing, structural, and blast components of the building. Each of these components will need to be reviewed and approved using detailed pdf files. These drawings will call out the placement and specifications for each of these elements, which were not detailed on the floor plan.

THIRD-PARTY APPROVAL FOR BLAST-RESISTANT BUILDINGS

Each build-site is different as far as requirements for blast-resistant buildings. Some states have strict environmental guidelines (California comes to mind), some follow another set of standards, like OSHA or other federal, local, or regional guidelines. 

Your blast-resistant building manufacturer will be responsible for ensuring that the building meets all requirements of the local authority having jurisdiction (LAHJ) and will set up any third-party reviews that need to happen. 

These requirements could add things like fire sprinklers, devices to improve air quality or emissions, or any number of details meant to protect the occupants of the building. It is the responsibility of the vendor to know and expect these requirements.