Regulation 11 Communication
The duty holder shall make appropriate arrangements—
for giving warning of an emergency, by audible and, where necessary, visual alarm systems, to all persons on the installation; and
for the purpose of emergency response, for communication between—
persons on the installation;
the installation and persons not on it and engaged in activities in connection with it; and
the installation and persons beyond it;
and shall ensure that, so far as is reasonably practicable, the arrangements are capable of remaining effective in an emergency.
Subject to paragraph (3), the duty holder shall ensure that—
an illuminated sign provided pursuant to paragraph (1)(a) is—
in the case of a warning of toxic gas, a red flashing sign; and
in all other cases, a yellow flashing sign; and
an acoustic signal provided pursuant to paragraph (1)(a) is—
in the case of a warning to prepare for evacuation, a continuous signal of variable frequency;
in the case of a warning of toxic gas, a continuous signal of a constant frequency; and
in all other cases, an intermittent signal of a constant frequency.
Where an illuminated sign or acoustic signal is in lawful use immediately before the date of coming into force of these Regulations, but it does not meet the requirements of paragraph (2), it shall be sufficient compliance with that paragraph if a change to a sign or signal so complying is made before 20th December 1997.