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Review by (2014-01-02)

Petzl Sirocco Helmet Review: Is it safe to go ultralight?

Last year, Petzl came out with the revolutionary, ultra-light Sirocco climbing and mountaineering helmet. What's so special about it? Well, it is by far the lightest climbing helmet on the market, has a very different foamy look to it, and only comes in one color which is bright orange. Petzl claims that you will not even notice wearing it. I can already confirm that this statement is absolutely correct. The Petzl Sirocco is incredibly light. Ultra-light freaks, speed climbers, and people who love flashy colors have been praising it in various blogs. Nevertheless, one big question remains: Is the Petzl Sirocco really safe? Or is there a trade-off between its light weight and overall safety?

What is the difference between the Sirocco and other ultralight helmets?

First things first. Let's compare the Sirocco with similar light helmets in its class:

Weight and certification comparision of ultralight climbing and mountaineering helmets
Weight and certification comparision of ultralight climbing and mountaineering helmets

The Sirocco only weighs 165g in size 2, which is roughly 20% less than the Black Diamond Vapor, the second lightest helmet on the market. However, looking at the table above, we notice that the Petzl Sirocco is CE EN 12492 and UIAA 106 certified while the Black Diamond Vapor only passes the CE EN 12492 certification. The CE EN 12492 is a standardized certification for climbing helmets from the European Committee for Standardization. The UIAA 106 is based on the EN 12492 with almost identical testing setups but requires 20% less impact force on the climber's head for some tests and is therefore more strict. The following graphic displays some of the certification requirements:

CN EN12492 and UIAA helmet ceritifcation requirements and tests
CN EN12492 and UIAA helmet ceritifcation requirements and tests

Physics behind the CN and UIAA helmet certifications:

The CE test requires that a spherical 5kg (11lbs) object which falls vertically from an elevation of 2m (6ft) will not cause a force of more than 10kN (1000kg, 2200lbs) on the head of the climber. Neglecting air drag, the object would hit the helmet with a speed of 6.2m/s and have a kinetic energy of 92J. The same kinetic energy would be reached by a 1kg object falling from 10m, or a 0.3kg object falling from 30m. In order to reduce the (average) impact force of this object to less than 10kN, the object has to travel at least another 0.01m (1cm, 0,4in) after impact. For an impact force of less than 8kN (UIAA) the object has to travel more than 0.012m. The helmet has to absorb most of the object's kinetic energy by deformation while the object keeps on traveling without breaking. Helmets only need to be able to absorb 25% of this energy on their front, side and rear in order to get certified. So, you better never look up to see what's coming down.

Anyways, what do all these numbers mean?

Well, if a junk of ice, a little bit bigger than the size of a gallon of milk, falls on your helmet from 2m above, you will survive. A piece of granite of similar size falling from 2m would cause 2.5times the maximum impact force since it is heavier. You or your helmet might not survive. You will probably survive a piece of ice about the size of a 1L bottle falling from 10m above, but not a piece of granite. However, you might survive a piece of granite which is the size of a can of coke.

Black Diamond Vapor vs. Petzl Sirocco

Considering the fact, that the Black Diamond Vapor is not UIAA certified, it is pretty safe to assume that it barely passed the CE certification. Furthermore, I suspect that ultralights helmets of similar construction (EPS liner with Polycarbonate shell) and similar weight, usually barely pass the UIAA certification. A few extra gram of foam seem to be necessary to reduce the impact forces in order to meet the stricter UIAA requirements. I think that EPS-Polycarbonate helmet constructions are close a physical limit in terms of weight reduction.

So what is the secret of the Petzl Sirocco? Why is it up to 40% lighter and still CE and UIAA certified?

The answer is Expanded Polypropylene (EPP) foam. EPP has been becoming very popular with hobbyist who build model airplanes in recent years. It is also a material of choice for car bumpers due to its ability to absorb huge kinetic impacts without breaking. EPP is a memory foam which returns to its original shape after bending or impacting it. So even if you like to torture your helmets there is a good chance your Petzl Sirocco will have very little sign of wear after some abusion and will sell for a good price on ebay.

Front view of the ultralight Petzl Sirocco climbing helmet. Made from EPP foam.
Front view of the ultralight Petzl Sirocco climbing helmet. Made from EPP foam.

What's the difference between EPS and EPP?

EPP is stronger than EPS and slightly heavier. It is more ductile, does not break as easily as EPS and therefore can absorb more kinetic energy by deformation. To achieve the same, EPS helmets need an extra polycarbonate hardshell layer in order to distribute impact forces over wider foam area and are therefore heavier.

What are the downsides of EPP and EPP helmets?

The downsides of EPP are that it is about 3.5times more expensive than EPS. It is very difficult and expensive to sand and to give it a nice finish look, which raises production costs. And it is not easy to color it. So, you better start liking that bright orange look of the Petzl Sirocco, since I don't expect a great variety of colors in the future. But most important of all, EPP does not have a good structural strength compared to EPS. It bends much more easily. In order to achieve sufficient stiffness, strengthening ribs were integrated into the design of the Petzl Sirocco which make the helmet appear kind of high on the head.

Strenghtening rips are part of the Sirocco design the overcome the structural weakness of EPP foam. The helmet sits high on the head.
Strenghtening rips are part of the Sirocco design the overcome the structural weakness of EPP foam. The helmet sits high on the head.

EPP has been used for bicycle and skateboard helmets in the past but does not seem very common anymore. I suspect that the strict CN certification regulations for bicycle helmets have something to do with that. During a bicycle crash the distance between the chin strap and the chin cannot be extended by more than 1.5cm to prevent the helmet to fall off. Due to their poor structural strength EPP helmets might not be stiff enough to easily fulfill this criteria. I wouldn't recommend hitting your local MTB freeride trail with your Sirocco. And always tighten your chin straps a little bit more than what you are used to.

Should you buy the Petzl Sirocco?

I say: YES! Well, the Sirocco ain't cheap, it ain't beautiful, and it ain't useful for really dangerous routes with lots of ice and rocks coming down. However, none of the ultralight helmets from other manufactures are. But man, the Sirocco is light. You will wear it every time, since you won't feel it and you won't overheat anymore. Without having it professionally tested, I think that the Sirocco is just as safe, or even a little bit safer than other ultralight climbing and mountaineering helmets in its category.

The magnetic chin strap clip works really well, even with big gloves.
The magnetic chin strap clip works really well, even with big gloves.

 

Our rating: 4.5 out of 5 stars

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