When respiratory protective devices are combined with hearing protectors, the head band of ear muffs may be incompatible (DGUV Regel 112-194 (to date: BGR/GUV-R 194) governing the use of hearing protection, January 2015, Sections 3.1.3.1.3, 3.2.1.6 and 3.3.12 at www.dguv.de/fb-psa, in German).