Morlandg. Tell your friend not to use the appliance until a qualified person fixes it. It might kill them in it’s present state.
Extract from internet:-
Carbon monoxide (CO) is poisonous. CO is an odorless, colorless and tasteless gas that can make you sick or, under some circumstances, cause death. Carbon monoxide occurs when fuel does not burn completely. To avoid CO hazards, make sure your appliances are properly installed, cleaned, maintained and vented.
The sources of carbon monoxide can include improperly vented cooking and water heating appliances, auto exhaust, blocked chimney flues and malfunctioning fuel-burning appliances.
Indications that carbon monoxide may be present in your home or building include the following:
- Black soot on or near registers, flues, furnace filters, burners or appliance access openings;
- Condensation on windows or interior walls (condensation on widows can also be caused by humidifiers or vaporizers);
- A yellow flame (instead of a blue flame) on appliance burners;