Look for your setting's policies and procedures
Look at your Local Council website for their procedures and advice.
Also see this:http://publications.environment-agency.gov.uk/PDF/GEHO0111BTJK-E-E.pdf
For gas see here:http://www.gassaferegister.co.uk/help/gas_emergency.aspx
The most obvious answer would be to keep gas appliances clean, well ventilated, and regularly serviced to ensure their safe working order.
Hope that helps