a. that the location of other signs or other light or sound sources does not affect the visibility or audibility of the signs or signals required pursuant to these regulations; b. that several signs are not placed near each other; c. that light signals that can be confused are not used at the same time; d. that one light signal is not used near another light source of a similar type; e. that two or more acoustic signals are not used at the same time; f. that acoustic signals are not used if background noise can prevent the signal from being perceived; g. that signs or signalling devices are easy to understand and clearly visible in relation to the dangers of which they warn; h. that a necessary number of signs or signalling devices are installed according to the degree of danger or risk, or the zone to be covered; i. that signs and signalling devices are inspected before they are put into operation and subsequently regularly cleaned, maintained, inspected, repaired and, if necessary, replaced to ensure that they work correctly and as intended; j. that signs that require an energy source are provided with an emergency power supply in case of a power failure, unless the risk disappears with the power failure; k. that the initiation of light and acoustic signals indicates when a required action starts. The light and acoustic signals must last for as long as the action requires; l. that light and acoustic signals are reset immediately after each use; m. that measures are taken to supplement or replace the relevant signs where the hearing or sight of affected employees is impaired, for example as a result of wearing personal protective equipment; n. Areas, rooms or enclosures used for storage of large quantities of hazardous, flammable or explosive substances or mixtures must be indicated by an appropriate safety sign chosen among those illustrated in Section 5-7 (2) or marked as provided for in Section 5-13, unless the marking on the individual packaging or container is sufficient for this purpose. If there is no suitable safety sign in Section 5-7 to warn against hazardous chemicals or mixtures, the relevant hazard pictogram must be used as provided for in the Regulations of 16 June 2012 No 622 on the classification, labelling and packaging of substances and mixtures (CLP); cf. Regulation (EC) no. 1272/2008 Annex V.