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Guidelines For Selecting Safety Helmets: Three Critical Aspects to Consider

Choosing the right helmet can be a daunting task. Over the past decade, an unprecedented variety of helmets has been introduced differing in style, price point, compliance with standards and manufacturer’s claims of improved protection.

Selecting the best helmet is further complicated by the scarcity of test data that provide evidence-based guidance. Let’s focus on guiding three aspects critical for selecting helmets that deliver superior head protection: brain protection, lateral protection (Type II) and helmet retention.

Brain Protection

Brain protection has been the blind spot in helmet design. A September 2023 article in Occupational Health & Safety stated that the current helmet standards must be updated to account for rotational motion, which is the key cause of concussions on construction job sites.

There are two different types of head injuries, namely skull fractures and brain injuries.

Fracture of the hard but brittle skull is caused by a straight impact, similar to the straight impact one would induce to crack a brittle eggshell. A rigid helmet shell combined with an impact-absorbing liner or suspension greatly reduces the skull fracture risk by decreasing the force of a straight impact on the skull.

Conversely, brain injury is mainly caused by head rotation in response to an impact. Head impacts typically cause a short but forceful head spin that twists the brain and shears the soft brain tissue. Similar to severing nerves of the spinal cord, the shearing of brain tissue causes irreversible damage that may lead to life-long suffering with staggering financial implications.

Brain injuries can range from mild concussions to severe traumatic brain injuries, whereby the cost associated with a single work-related traumatic brain injury typically exceeds $1 million. This staggering human and financial cost of brain injury is often caused by rather simple and frequent events. Over 60 percent of work-related brain injuries are caused by simple slips, trips and same-level falls.

Most interestingly, over 90 percent of such brain injuries occur in the absence of a skull fracture, which further confirms that the soft brain is injured by a distinctly different mechanism than the hard skull. However, this critical vulnerability of the brain to rotational forces is neither considered in standardized helmet tests nor accounted for in traditional helmet designs.

Sports helmets have recently adopted technologies to shield the brain from rotational force. One technology, called multi-directional impact protection system (MIPS), is a plastic sheet that seeks to reduce the transmission of rotational force by slipping during impact. These MIPS slip liners can be retrofitted into existing helmet designs and are available in a wide range of bike and snow helmets.

More recently, rotation-damping technologies were introduced in safety helmets, offering better protection from rotational forces than modern safety helmets. And since over 50,000 work-related brain injuries are admitted to hospitals in the U.S. each year, selecting helmets that have rotation-damping technology should be a primary consideration when selecting a new helmet.

Lateral Protection

The strap suspension of traditional helmets is a directional design. It is designed to absorb crown impacts, but it was found “practically useless against side, front and rear impacts” in a 1987 helmet test study by the Journal of Occupational Accidents. The authors of that study properly concluded that a redesign is necessary since the majority of impacts are lateral while only 15 percent of impacts occur to the helmet crown.

The US ANSI standard Z89.1 properly recognized this shortcoming and added a Type II designation, whereby Type II-certified helmets are also tested for their ability to absorb lateral impacts. A recent publication documented that most helmets from leading brands still only delivered Type I “crown only” protection. This shortcoming was noted for hard hat-style helmets as well as for “climbing-style” safety helmets.

Selecting an ANSI Type II helmet is therefore important to provide protection against the most frequent lateral impacts.

Helmet Retention

A helmet can only provide protection if it stays on the head during a fall. Chin straps can readily prevent a helmet from falling off the head. The US standard ANSI Z89.1 does not require chin straps but requires retention testing of chin straps if they are supplied with the helmet. In contrast, the European standard EN 12492, titled “Helmets for Mountaineers” requires chin straps. This standard is often used for “climbing style” safety helmets since it requires chin straps as well as lateral impact testing.

However, lateral impact testing is far less stringent in EN 12492 than in the US standard ANSI Z89.1 since it utilizes a 20 percent lower impact energy, a flat rather than a focal impactor, and since the test area does not extend as far down to the brim as in the U.S. standard. For the best head protection, select helmets with chin straps. And while an EN 12492 certification will ensure the presence of a chin strap, this standard is no substitute for meeting ANSI Z89.1 Type II performance.

Conclusion

When choosing a helmet based on available evidence of performance, here’s a quick checklist of what to consider:

  1. Choose a helmet with a rotation-mitigating technology to reduce the risk of brain injury. Since rotational forces can readily be measured in tests, manufacturers should provide data on the relative benefit of their technology compared to standard helmets.
  2. Choose a helmet that is ANSI Type II rated to protect from lateral impacts which occur far more often than crown impacts.
  3. Choose a helmet with chin straps to ensure the helmet remains on the head during impact.

In addition to these impact performance criteria, factors about user satisfaction are equally important for helmet adoption, such as comfort, weight, heat and style. In regard to style, the industry-led promotion of presumably safer “climbing-style” safety helmets over traditional hard hats is not supported by data. Helmets should be selected based on performance, independent of a particular helmet style.

Source: OHSOnline

Image: Freepik

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