Depending upon the hairstyle and hair structure, hair may increase dimensions involving a landmark on the head. Examples of such dimensions are the body height and head circumference.
For dimensions relevant to safety, the influence of hair upon the body dimensions must not therefore be ignored.
Different hairstyles and hair structures (e.g. curly hair) may modify the body dimensions, particularly when no additional headgear is worn. This must be taken into account during standardization and design work.
The body height is measured by a standardized procedure on the highest bony point on the skull (the vertex). The hair must be prevented as far as possible from influencing the measured value of the body dimension. A similar procedure is followed for measurement of circumferential head measurements. Depending upon fashions, the hair may result in an increase of over 50 mm in the values for the body height, height sitting (trunk length + head height), head length (depth) and head height, particularly for women. In the context of body dimensions (such as the body height for men and women), this value generally lies within the 95th percentile for men for the body dimension concerned (e.g. P95 for the body height of men = 1,855 mm, P95 for the body height of women = 1,720 mm). If approximately 50 mm is added to the height for women in order to allow for the hairstyle, the result is still within the range for the body height of men (DIN 33402-2). Changes in fashions may however also influence the corresponding body dimensions of men.
For dimensions that affect or involve the finger lengths (e.g. the hand length), an allowance of a few millimetres, or possibly higher values where dictated by fashions, must be added for the fingernails, since they extend beyond the fingertips. This is relevant primarily to the design of control elements that are to be actuated by individual fingers, and during the observance of relevant safety clearances.