Carbon monoxide is produced from the partial combustion of carbon-containing compounds such as gas. It is silent, colourless, odourless and potentially lethal. To prevent against carbon monoxide exposure you should ensure gas appliances, such as your boiler, are installed and serviced regularly by a CORGI registered engineer. In addition, all businesses have a responsibility to ensure appliances meet the Gas Safety (Installation and Use) Regulations 1998 and The Health and Safety at Work Act 1974.