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Head Protection PPE: What’s Available and Why Rotational Motion Matters

By Joe Brandel, Contributor

The latest research reveals that rotational motion poses a serious risk to worker health.

As an industry, construction consistently ranks as one of the most dangerous in the U.S.[1] The construction industry was responsible for about one in five workplace fatalities in 2021, and several common types of workplace accidents pose heightened risk of injuries for those working in this sector as well. For example, 46.2% of all workplace accidents resulting from slips, trips, and falls in 2021 were in the construction industry.[2]

The danger that slips, trips, and falls present should not be overlooked, with one of the biggest risks associated being traumatic brain injury (TBI). Falls lead to nearly half of all TBI hospitalizations.[3] Even though these risks across job sites aren’t likely to change any time soon, the head protection available to workers in the industry also hasn’t changed much in the past hundred years despite scientific advancements.

The Start of Hard Hats

The U.S. was first introduced to hard hats during World War I, when the nation was building ships for the Navy. The very first version in 1919, known as the Hard-Boiled Hard Hat, was made from boiled leather and metal. In 1928, inner suspensions were added, designed to absorb impacts from dropped objects. Helmets made of aluminum and fiberglass were developed in the 1930s and 40s, followed by the introduction of the plastic hard hat in 1951.

While the science behind helmets and brain safety has evolved – and helmets have experienced updates including attachments for face shields, integrated eyewear and hearing protection, and rated chinstraps – there have been relatively few significant changes since they were first developed.

Head Protection PPE Today

Currently, under the ANSI/ISEA Z89.1 standard, there are two types of helmets available: Type I and Type II. Both are effective in certain situations, but it’s important for workers to understand how they’re designed to work, and their differences.

Type I helmets are designed to protect workers from the impact of forces directly to the top of the head. Type II helmets are meant to protect workers from side (lateral) impacts to reduce the force of impact resulting from a blow which may be off center, in addition to the top of the head. Additionally, helmets are divided into three classes: G, general; E, electrical; and C, conductive.

Under the ANSI/ISEA Z89.1 standard, helmets undergo five performance tests to determine their classification. These include flammability, force transmission, impact energy attenuation, apex penetration, and electrical insulation. Force transmission tests are used to conclude if helmets reduce the force of a linear impact to the crown of the head, and energy attenuation tests are used to determine if helmets can reduce the force of linear impacts to the front, rear, and sides of the helmet.

Yet under the current standards, these tests only determine the impact of linear forces on the wearer’s head and overlook one of the main causes of concussions.

Understanding Rotational Motion

TBIs impact the function of the brain. These injuries can lead to short-term impacts, such as how someone moves, communicates, or cognitive skills, or long-term impacts, such as disabilities or even death.

In the construction industry, workers are at risk of developing TBIs particularly due to the common types of accidents they face. Slips, trips, and falls can be especially harmful. When someone’s head makes impact with the ground or an object, research shows that this often occurs at an angle, therefore exposing them to rotational motion.

Rotational motion is the combination of rotational energy (angular velocity) and rotational forces (angular acceleration), and can result from oblique impacts to the head. As this rotation is transferred to the brain, it can potentially result in shearing and subsequent damage to axons in the brain, or the cable transmitters of neurons.[4]

Experiments and numerical computer simulations indicate that the brain is more sensitive to rotational motion than linear motion when it comes to concussions.[5] In other words, if rotation is a contributing factor, concussions can occur with seemingly light impacts more easily than from linear impacts alone.

These differing types of impacts can lead to different types of injuries. Rotational motion can cause diffuse injuries, including diffuse axonal injuries and subdural hematomas. Linear injuries, injuries that result from straight impacts to the head, can cause focal injuries, including fractures and contusions. Oftentimes, linear and rotational motion occur simultaneously, which can lead to potentially greater risks of injury.

Why This Matters

As of now, there have been no tests performed in the current standards to test the impact of rotational motion on the helmet wearer’s head. While these types of tests have been taken into account in the moto industry, the construction industry has yet to utilize such tests.

Industry workers must understand the risks associated with common job site accidents, TBIs, and how these can lead to serious long-term injuries and even death. Having a deep comprehension of the PPE that is available, and how it can potentially protect against the risks of the job is critical. While many employers require that Type II helmets be used, which can include chinstraps, none of the current standards mandate helmets that work to address rotational motion. Workers should consider using helmets equipped with a system addressing rotational motion, such as the Mips® brain protection system for industrial safety helmets, designed to help redirect rotational motion away from the head, in the case of certain angled impacts.

Despite head protection options and standards not changing significantly over the past few years, research indicates that rotational motion poses a serious risk. In an effort to overcome this risk, it’s crucial that workers know about these health threats and the PPE available to address them.

Joe Brandel is the Business Development Manager of the NA Industrial Safety Market, Mips (




[4] Gennarelli (1987). “Directional dependence of axonal brain injury due to centroidal and non-centroidal acceleration,” in Proceedings of the 31st Stapp Car Crash Conference (Warrendale, PA: Society of Automotive Engineers).

[5] Kleiven, S (2007). “Predictors for traumatic brain injuries evaluated through accident reconstructions,” Stapp Car Crash J, vol. 51, pp. 81–114, Oct. 2007.

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