The location of boiler is somewhat irrelevant to the CO, even when the boiler/burner is completely sound proof the products of combustion still exist through flue terminal and if the CO is high then this can affect anyone breathing it in, it only takes around 50/70ppm to be affected and in the region of around 150ppm can be fatal, this varies from individual as well, someone with underlying health conditions can be more susceptible than others. Also carbon monoxide testers need to be replaced from time to time.
Yes please keep us posted. If the problem is ongoing when the weather warms then we can take another look 🙂.
Yes please keep us posted. If the problem is ongoing when the weather warms then we can take another look 🙂.