Blast proof doors are designed to resist explosive blasts and protect people and property from the damage from blast waves, including flying fragments, fire, and toxic fumes. Since we can’t entirely eliminate the threat of explosions on worksites, it’s crucial to ensure buildings and their windows, roofs, and doors can withstand blasts.
People often ask what the best material is for a blast proof door. But there’s a problem with that question.
It’s more accurate to describe materials as “blast resistant” rather than “blast proof” since nothing is permanently impervious to damage. Every material has its breaking point. In a blast resistant building, the goal is to keep people as safe as possible and give them enough time to remove themselves from a dangerous situation.
We already know the best option for blast resistant buildings is steel. Some might turn to iron when it comes to blast-resistant doors because they are often seen on buildings requiring heavy security. But it would be incorrect to assume an iron door is strong enough to absorb a blast. For maximum protection from the heat and pressure associated with explosions, you need a door made of an alloy like steel.
What Can Iron Doors Withstand?
Iron doors can be used in demanding environments. They are designed to be resistant to rust, severe weather, and rot. Iron doors can also be designed with thermal insulation to keep heat in or out and they hold up well to water, wind, and high pressure. But while iron and steel are quite durable, iron is more susceptible to corrosion due to its tendency to react with oxygen and moisture.
While iron doors provide a good level of protection from natural elements, they are rarely used for blast proof or blast resistant doors. Instead, blast resistant doors are manufactured from aluminum, concrete, timber, and steel. Steel is the material of choice for it bends to absorb large amounts of pressure.
Do I Need Blast Resistant Doors?
Blast resistant doors are used in industries where there is some risk of explosion or high-pressure blast. These can include refineries, chemical plants, hazardous material storage facilities, pharmaceutical and other research labs, bioscience buildings, nuclear power stations, airplane hangars, and military installations.
While blast resistant doors do not fall under any official building code, international standards act as guidelines for assessing their safety; for example, SDI-133-16 Guideline for Specifying Steel Doors and Frames for Blast Resistance, and the ASTM F2247-18 Standard Test Method for Metal Doors Used in Blast Resistant Applications (Equivalent Static Load Method). They are required in many government buildings, including those belonging to the U.S. Department of Defense (DoD), Veterans Affairs (VA), Department of State (DOS), and the General Services Administration (GSA).
Blast resistant doors are commonly made of steel, including their frames and hardware. That’s because steel excels in all four major strength categories: tensile, compressive, yield, and impact.
Why Steel is the Best Material for Blast Resistant Doors
When specifying criteria for a blast resistant door, companies should look for the following information:
- Peak blast pressure (measured in psi)
- Blast duration or impulse (measured in psi per millisecond)
- Rating for post-blast event damage (ranging from Category I for no permanent damage to Category V for catastrophic damage). Blast doors should be rated a Category I to III
When comparing blast resistant doors, steel tops iron doors in every category.
The Components of Steel
Ironically, the main component of steel is iron, followed by carbon. Steel would corrode just like iron if not for adding elements such as chromium, which helps form a protective surface.
Steel is also made of silicon, carbon, nickel (to improve flexibility), nitrogen (to improve ductility and tensile strength), and manganese. These alloys aren’t consistent across different types of steel, so it’s crucial to know what has been added to steel and in what amounts to determine whether it’s appropriate for specific construction use.
The Benefits of Steel
Tensile strength may be one of steel’s biggest benefits. It can expand without breaking, absorbing large amounts of pressure. It doesn’t crack, twist, or rot. This is measured in pounds per square inch or psi for blast resistant doors. Steel doors can measure anywhere from 1 to 50 psi.
Other benefits of steel blast resistant doors include their low cost of ownership, their ability to be repaired in the field, and their longevity. Steel is also the only door material that offers a three-hour fire rating.
Finally, steel is one of the most sustainable building materials since it can be recycled. Specifying steel in construction can help companies achieve LEED credits and compliance with International Green Construction Code (IGCC) requirements.
Iron vs. Steel Blast Doors
When it comes to blast resistant doors, both iron and steel are durable choices. However, iron doors are much more likely to be used for security than for blast mitigation.
The required use of steel doors in many government buildings means they're more common, as well as more likely to undergo strict quality control, making them an ideal choice for blast resistant buildings.