Specifications for hurricane shutters and impact windows often include a phrase like "tested to ASTM E1886/E1996, Missile Level E." For architects, facility managers and owners, that short line carries a lot of meaning. This article explains the two ASTM standards, the missile levels they define, and why Level E is associated with essential facilities such as hospitals and emergency operations centers.
Two Standards That Work Together
ASTM E1886 is a test method. It describes how to test exterior windows, curtain walls, doors and impact protective systems such as shutters: how to fire missiles at the specimen, where to aim them, and how to apply cyclic pressure afterward.
ASTM E1996 is a specification. It tells you what level of performance is required: which missile to use, how fast it must travel, and how much cyclic pressure the specimen must withstand after impact, based on the building's wind exposure and how important the building is.
In short, E1886 explains how to test and E1996 explains what the product has to survive. That is why they usually appear together in specifications and product approvals.
Small Missiles and Large Missiles
The standards recognize that debris in a hurricane comes in many sizes. Roof gravel and small fragments travel high up a building, while larger debris such as lumber is more likely to strike the lower floors. ASTM E1996 therefore uses two kinds of missiles:
- Small missiles: steel balls fired at high speed, representing gravel and small fragments. Missile Level A uses small missiles.
- Large missiles: pieces of 2x4 lumber of different weights and speeds, representing larger debris. Missile Levels B, C, D and E use large missiles of increasing severity.
Which missile applies depends partly on height above ground. Codes commonly require large missile protection for openings in the lower part of a building and allow small missile protection higher up, though the exact rules depend on the code in force.
The Large Missile Levels
For the higher large missile levels, the missile is a 9 lb 2x4 roughly eight feet long:
- Level D – the 9 lb 2x4 is fired at 50 feet per second (about 34 mph). This is the familiar "large missile" requirement for many buildings in high wind regions.
- Level E – the same 9 lb 2x4 is fired at 80 feet per second (about 55 mph). Because impact energy rises with the square of speed, Level E delivers roughly two and a half times the energy of Level D.
Levels B and C use lighter 2x4 missiles at lower speeds and apply to less severe wind zones. After impact, specimens must also pass cyclic pressure testing to show that the damaged product still resists the push and pull of hurricane winds.
Why Level E Is Tied to Essential Facilities
Codes and standards recognize that some buildings must keep working during and after a hurricane. ASTM E1996 includes enhanced protection for these essential facilities, and the Florida Building Code requires essential facilities outside the High Velocity Hurricane Zone to meet the Level E standard. Essential facilities typically include:
- Hospitals and other health care facilities with emergency treatment
- Fire, rescue and police stations and emergency vehicle garages
- Designated emergency shelters
- Emergency operations centers and communications centers
- Power generating stations and utilities needed in an emergency
- Buildings with critical national defense functions
For these buildings, a failed window is not just property damage. It can force an evacuation at the worst possible moment or take an emergency service offline. FEMA guidance for critical facilities and storm shelters reflects the same idea: these buildings deserve a higher level of protection.
One note on terminology: older editions of ASTM E1996 tied Level E to "Wind Zone 4". Later editions moved wind zone references into an appendix, so current specifications usually refer to the enhanced protection requirements and the missile level rather than the wind zone. Always check which edition your local code references.
How Level E Applies to Shutters
Shutters and other impact protective systems are tested on their own, mounted in front of a test opening. In addition to resisting penetration, the shutter must not deflect so far that it would strike and break the glass behind it. That is why product approvals for shutters specify a minimum separation from the glass. When a project calls for Level E, check that the shutter's test reports and approvals specifically list Level E, the opening sizes covered, and the separation required.
STORM SHIELD Hurricane Barriers use a perforated 14 ga. mill-galvannealed steel or 300 series stainless steel infill designed for ASTM E1886/E1996 Level "E" essential facilities protection. The system has been used on state and county emergency operations centers, hospitals and schools. See the features and specifications and the performance and testing pages, and request current test documentation for your project.
Testing Is Only Part of the Picture
A Level E test report shows that a product sample survived the test in a laboratory. To get the same performance on a real building, three more things must line up. First, the installed product must match the tested configuration: the same panel, frame, fasteners and anchors. Second, the anchors must suit the wall they are installed in, whether that is poured concrete, concrete block, wood framing or steel. Third, the opening sizes must stay within the limits covered by the test and approval. A careful installer, a clear set of approved drawings and an inspection by the building official close the gap between the lab and the job site.
Questions to Ask Your Supplier
- Which edition of ASTM E1886/E1996 was the product tested to, and at which missile level?
- Was the cyclic pressure test passed at the design pressures needed for my openings?
- What is the largest opening size covered at Level E?
- What minimum separation from the glass is required?
- Is the product also covered by a Miami-Dade NOA or Florida Product Approval? See Miami-Dade NOA explained.
Conclusion
Missile Level E represents the most severe large missile test in ASTM E1996: a 9 lb 2x4 at 80 feet per second, followed by cyclic pressure. It exists because some buildings must stay operational when a hurricane hits. If you are responsible for an essential facility, make Level E testing and the matching approvals a starting point for any shutter you consider. For more on protecting these buildings, read hurricane protection for schools, hospitals and EOCs.