A pressure relief device for venting an internally pressurized container such as an aerosol can has three sections, a concave annular outer area, a circular central area and an annular intermediate area connecting the concave annular area to the circular area. The three sections all have the same thickness. The central area has a center point and an arc shaped score line extending through 132.degree. to 138.degree., preferably 135.degree., about an arc center. The arc center is offset from the center point of the circular area by a distance of from about 0.290 inches. The score line has a depth of from 0.010 to 0.012 inches and is trapezoidal in transverse cross section. The intermediate area meets the circular area at an angle greater than 90.degree. and the intermediate area meets the concave annular outer area at an angle greater than 90.degree..

 
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> Aerosol device comprising a hair treatment composition, and hair treatment process

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