2.8 The Effects of Discomfort in Helmets
19
In South East Asia, excessive sweating and the resulting discomfort due to hot
and humid weather conditions discourage motorcycle riders from using helmets even
where it is mandatory by law. The space between the head and helmet is small, and
air velocities in this gap are also low. Hence, the rider is very uncomfortable due to
sweat, which is unable to evaporate and accumulates within the helmet.
2.8.1 Skin Temperature
Skin temperature is dependent on air temperature and the time spent in that environment. Weather factors such as wind chill and humidity contribute to causing changes
in skin temperature. The normal temperature of skin is about 37 °C. In general, the
temperature range at which a person feels comfortable is 29–34 °C. Above a temperature of 40 °C, the person will start feeling discomfort, and below 20 °C, there will
be loss of agility [46].
It is essential that the core body temperature is maintained at a certain level to
establish thermoregulatory equilibrium. Although thermal equilibrium is a necessary condition for thermal comfort, it is not the only condition. Both skin-surface
temperature (T sk ) and core temperature (T c ) affect thermoregulatory equilibrium. It
was found that the ratio of the contribution of skin-surface temperature (T sk ) and
core temperature (T c ) to thermal comfort is approximately 1:1 [47].
2.8.2 Sweating
Perspiration or sweat is the production of a fluid from the body consisting primarily
of water as well as various dissolved solids (chiefly chlorides) that is excreted by
the sweat glands in the skin of mammals [48]. Sweat also contains the chemicals
or odourants 2-methylphenol (o- cresol) and 4-methylphenol (p-cresol) as well as a
small amount of urea.
In humans, sweating is primarily a means of thermoregulation [49]. Evaporation
of sweat from the skin surface has a cooling effect due to the latent heat of evaporation
of water.
Hence, in hot weather or when the individual’s muscles heat up due to exertion,
more sweat is produced. Sweating is also increased by nervousness or nausea and
decreased by cold.
There are two situations in which our nerves will stimulate sweat glands, making
us sweat: during physical heat and during emotional stress. Emotionally induced
sweating is generally restricted to palms, soles and sometimes the forehead, while
physical heat induced sweating occurs throughout the body [50].
An increase in air velocity increases sweat evaporation and thus results in a reduction of discomfort felt by the rider. The air velocity inside the helmet can be improved
by providing holes in the helmet (similar to bicycle helmets). However, these holes
19
In South East Asia, excessive sweating and the resulting discomfort due to hot
and humid weather conditions discourage motorcycle riders from using helmets even
where it is mandatory by law. The space between the head and helmet is small, and
air velocities in this gap are also low. Hence, the rider is very uncomfortable due to
sweat, which is unable to evaporate and accumulates within the helmet.
2.8.1 Skin Temperature
Skin temperature is dependent on air temperature and the time spent in that environment. Weather factors such as wind chill and humidity contribute to causing changes
in skin temperature. The normal temperature of skin is about 37 °C. In general, the
temperature range at which a person feels comfortable is 29–34 °C. Above a temperature of 40 °C, the person will start feeling discomfort, and below 20 °C, there will
be loss of agility [46].
It is essential that the core body temperature is maintained at a certain level to
establish thermoregulatory equilibrium. Although thermal equilibrium is a necessary condition for thermal comfort, it is not the only condition. Both skin-surface
temperature (T sk ) and core temperature (T c ) affect thermoregulatory equilibrium. It
was found that the ratio of the contribution of skin-surface temperature (T sk ) and
core temperature (T c ) to thermal comfort is approximately 1:1 [47].
2.8.2 Sweating
Perspiration or sweat is the production of a fluid from the body consisting primarily
of water as well as various dissolved solids (chiefly chlorides) that is excreted by
the sweat glands in the skin of mammals [48]. Sweat also contains the chemicals
or odourants 2-methylphenol (o- cresol) and 4-methylphenol (p-cresol) as well as a
small amount of urea.
In humans, sweating is primarily a means of thermoregulation [49]. Evaporation
of sweat from the skin surface has a cooling effect due to the latent heat of evaporation
of water.
Hence, in hot weather or when the individual’s muscles heat up due to exertion,
more sweat is produced. Sweating is also increased by nervousness or nausea and
decreased by cold.
There are two situations in which our nerves will stimulate sweat glands, making
us sweat: during physical heat and during emotional stress. Emotionally induced
sweating is generally restricted to palms, soles and sometimes the forehead, while
physical heat induced sweating occurs throughout the body [50].
An increase in air velocity increases sweat evaporation and thus results in a reduction of discomfort felt by the rider. The air velocity inside the helmet can be improved
by providing holes in the helmet (similar to bicycle helmets). However, these holes