got called out tonight to a suspected leak on a gas fire installed yesterday(not mine)leak found on new pipework,sorted out leak on pipework and relit fire,i noticed that there was sooting on the coals and the back of the coal panel,did fga on it and the reading was 1574ppm,fga went ape,anyway i isolated fire and issued a warning notice,advised customer to contact the place they brought it from to sort this out,they had recommended the installer they use,i have not come across this before and would appreciate your thoughts and what action i should take.thanks in advance