1. The Cushion on a School Chair Is Actually a Disaster Prevention Hood
In many classrooms, a cushion-like object is attached to the back of school chairs. It is not uncommon for students to discover that this object is actually a disaster prevention hood. Many of these hoods are designed to be folded and stored, allowing them to serve as seat cushions or backrests during normal times without taking up extra space [2].
A report by the Kahoku Shimbun connects this dual use to the concept of "phase-free" living. This idea suggests that there should be no separation between normal times and emergencies; instead, one should be prepared for disasters as part of daily life. The newspaper notes that this approach has been emphasized in recent years [2]. If a cushion can become a head protector, what is inside it that allows it to do both?
2. How a Disaster Prevention Hood Is Made: Two Layers of Fabric and Cotton
A disaster prevention hood is made by joining two layers of fabric and filling the space between them with cotton or other cushioning materials to form a shape that fits over the head [1]. Cotton contains many air pockets. When an object hits the cotton, it compresses and absorbs the force. This is the same reason seat cushions feel fluffy, though this explanation is general and not directly proven by hood test results.
According to available materials, these hoods are disaster goods designed to protect the head from the impact of light falling objects and sparks from fires. The items assumed to fall are light things like glass shards, light bulbs, and books [1]. It is clearly stated that these hoods are not suitable for heavy falling objects or strong impacts, meaning they are not tools that "prevent everything." If they are suited for "light things," how does this appear in test numbers? Comparing test conditions reveals that hoods and helmets use different measuring standards.
3. Impact Test Heights of 10 cm and 1 m for Disaster Prevention Hoods
According to an explanation by the disaster prevention blog Pioma, disaster prevention hoods have certification standards from the Japan Fire Retardant Association. The test involves placing the hood on a model of a human head and dropping a 5 kg weight from a height of 10 cm. The impact must be 7.4 kN or less [1].
In the same explanation, disaster prevention helmets follow standards from the Ministry of Health, Labour and Welfare. A 5 kg weight is dropped from a height of 1 m, and the impact must be 4.9 kN or less [1]. The drop height is 10 cm for hoods and 100 cm for helmets, a difference of ten times.
It is too early to conclude that "helmets are much stronger" based on these numbers alone. Hoods are certified for flame retardancy, while helmets follow labor safety standards. These are different systems, and these figures come via a blog. The standard values of 7.4 kN and 4.9 kN cannot simply be compared side by side. However, the fact that hoods are tested at 10 cm and helmets at 1 m shows that their underlying philosophies differ.
In a test by the National Consumer Affairs Center of Japan, reported by the Kahoku Shimbun, hoods were said to reduce impact by about 50%, and by about 80% depending on the product. On the other hand, it was pointed out that helmets have much higher impact absorption than hoods [2]. Since this is an indirect report through a newspaper article, the numbers should be taken as rough estimates.
One system is for flame retardant certification, while the other is for labor safety standards. The test heights also differ, so direct comparisons are difficult.
If hoods are inferior in impact resistance, do they have other strengths?
4. How Hoods Protect the Face and Shoulders from Sparks and Glass
According to a disaster mitigation advisor, if looking only at the function of protecting the head from falling objects, a disaster prevention hood is "more than a hat but less than a helmet." However, a strength is that it covers the face and shoulders in addition to the head, protecting them from sparks falling during a fire or glass shards scattering from broken windows [2].
The shape that snugly covers the whole head is a strength that helmets do not have. However, the strength against sparks depends on whether the product has received flame retardant certification and varies by product. Imagining a scene where glass shatters and scatters, or where sparks fall, helps us understand the meaning of being able to cover the face and shoulders with fabric.
The strength against sparks is also related to the flame retardant system. A list of flame retardant products compiled by Sakai City includes disaster prevention hoods, their outer fabric, and fillings as separate categories [3]. Although hoods have a simple structure of fabric and cotton, both the fabric and the filling are subject to the concept of flame retardancy.
Seen this way, it is not that hoods or helmets are "better," but rather that the threats they protect against and the areas they cover are different. When and where did these hoods spread in schools?
5. How Disaster Prevention Hoods Spread as Preparation for the Tokai Earthquake
Disaster prevention hoods are said to have spread as preparation for the Tokai earthquake, starting in the 1970s, based on the air-raid hoods used at the end of the Pacific War [1].
The way they spread varied clearly by region. According to the Nikkei, as of the end of March 2012, public schools that had stockpiled disaster prevention hoods or helmets for children were about 60% in Tokyo and Kanagawa, and about 20% in Osaka and Hyogo [4]. This is a difference of about three times between 60% and 20%.
In Sendai, the Kahoku Shimbun published an article with the headline "Air-raid hoods reappear" about one year after the 1978 Miyagi-ken Oki earthquake. This article shows that some elementary schools had adopted hoods similar to air-raid hoods [2].
Hoods are not only for schools. According to Wikipedia, disaster prevention hoods were kept under the seats of members in the National Diet building, but they were replaced with folding helmets starting in 2017 [5]. This suggests that the choice between hoods and helmets has changed depending on the location and the philosophy behind the choice.
6. Comparing the Logic of Disaster Prevention Hoods and Helmets
If there is a disaster prevention hood at school or home, look at it. Observing the label, the seams, the feel of the cotton inside, and the parts that can be used as a cushion makes the content of this article visible.
Another good method is to look at disaster prevention tools at school or home and ask family members or teachers, "Why was this chosen?" It does not matter if it is a hood, a helmet, or another tool. Is it for falling objects, sparks, or storage space? The reason for the choice may differ depending on the region or school.
If you want to deepen your research, look at the original certification standards of the Japan Fire Retardant Association or the original test information from the National Consumer Affairs Center of Japan on children's disaster prevention hoods. This will reveal the conditions behind the numbers described in this article as "said to be."