How are closed vented (no exhaust to outside) hearth systems allowed? Wouldn't this cause carbon monoxide problems if incomplete combustion occurs? My fiance lives in a apartment that has one of these. The guy from the utility company was trying to regulate the gas pressure using the shutoff valve. Management said that the units get too hot when left on high. I guess this was his way of reducing the heat. The slightly closed the valve then took off the knob and put plumbers strap with a bolt around it. This was so tenants wouldn't touch it. I guess they thought it wasn't a good idea after I complained (even though they said it wasn't a code violation) because they removed the strap and replaced the knob. Now the shutoff valve is on. They put a heat sensing rod in the fireplace which is connected to two wires. I'm guessing it goes to the submeter valve. Is this correct??? It seems like it will shut off the gas if it gets too hot. The building only has one main gas regulator and then it is submetered by another company. Is there anything I should be concerned about.