I need to know if there is a test for sewer gas.  My family seems to get more headaches than normal – summer and winter. I am in the construction industry so I know some things.  My furnace has been replaced with a high efficiency unit with exhaust and outside air intake, so I don’t think it’s that.  Our home has a crawl space.  Sometimes I feel a slight burning in my eyes.  I have a carbon monoxide detector that hasn’t detected anything.  Could this be a sewer gas problem or could a mold problem have these signs?  We have a 2200 sq. ft. 2-story home.  I think I am getting good ventilation on my water heater vent.  What are your thoughts? -  Art, Illinois

            Let me respond to your questions by  addressing the symptoms you have reported, headaches and slight eye burning.  Headaches among all members of one’s family  associated with one’s house is not a normal situation.  This symptom can be result from exposures such as carbon monoxide (CO), formaldehyde and mold.  If there are no associated respiratory symptoms, it is unlikely to be formaldehyde or mold.  That makes CO a primary suspect. 

            You indicate that your CO detector does not indicate the presence of CO.  Whether you get a positive response on a CO detector or not depends on the type of detector and its sensitivity.  In alarm-only detectors the CO level must be high enough to trigger the alarm.  If the threshold for such an alarm is too high, you may be exposed to sufficient CO to get headaches without any knowledge that you are being exposed to CO. 

            In digital reading devices you have CO detectors that only record levels that are occurring at the time you are reading it.  In others there is a button you can push which records the highest CO level since you last reset it.  I recommend using such devices since CO occurs in episodes and such devices capture peak levels since you last reset it. A highly regarded (Consumers Union) CO monitor (Kidde 900-0076-00 Nighthawk Carbon Monoxide Detector) that has such a function is illustrated.

            The fact that you have a high efficiency furnace (with mechanical draft) and a natural draft hot water heater is a cause for concern.  In my experience back-drafting of flue gases with such a configuration is common.  You can tell this from water stains or corrosion that results from water vapor that fails to rise through the chimney and condenses in flue pipes.  If water vapor fails to rise, then so do CO and other flue gases.

            The combustion gases contain a variety of combustion byproducts including aldehydes.  Aldehydes can, of course, cause eye irritation. 

            These digital images was taken in the garage of a homeowner who was experiencing morning nausea.  In them you can see a medium-efficiency mechanical draft furnace and a natural draft hot water heater.  Because of condensate-induced corrosion, the flue pipe above the draft hood of the hot water heater had to be replaced. Notice the bright shiny flue pipe connected to an older galvanized pipe section.  After installing a CO detector with a peak CO function, concentrations of up to 60 ppm were recorded during nighttime hours in the garage. Lower levels would have been expected in the house, levels that were not sufficient to trigger a CO alarm, but sufficient to cause low-level symptoms in a very sensitive homeowner.

             Ammonia in sewer cases can cause eye irritation. It is unlikely to cause headaches.