Ask The Experts


My house is for sale and was just inspected. The inspector said that my chimney was blocked and the water heater exhaust was coming into the house. I want to know why my carbon monoxide detector didn’t go off.

Assuming that your detector was not defective, the answer of course is that there was not enough carbon monoxide in the air to trigger the detector. This is not surprising for a couple of reasons. First, a clean burning gas appliance actually produces very little carbon monoxide (CO). CO is produced when combustion is poor due to misadjustment of the burner, impingement of the flame against a surface, or insufficient oxygen supply for proper combustion. A poorly adjusted flame, or an appliance in a location with insufficient makeup air can produce significant and potentially deadly amounts of CO. That’s why periodic professional inspection and testing of your gas appliances is so important. The exhaust gases in a clean burning appliance consist primarily of relatively harmless carbon dioxide and water vapor. Getting the exhaust gases out of the house is still important, but the exhaust may not be deadly.

The second reason that the alarm may not have sounded is that standard approved CO detectors aren’t actually very sensitive. They are calibrated to alert you to situations that are deadly, not to simply elevated, and only potentially harmful, levels. In fact, at the relatively low level of 40 parts per million, the standard CO detector will take one to six days to sound the alarm, if at all, but the EPA recommends a maximum exposure to 35 parts per million of only one hour. Some studies have shown health problems from chronic exposures as low as 5 parts per million. You can easily exceed recommended maximum carbon monoxide exposure without being alerted by the average detector.

It is our understanding that the insensitivity of CO detectors was allowed due to the relative inaccuracy of low cost units, and the likelihood of false alarms if they were calibrated for greater sensitivity. If you are interested in purchasing a much more sensitive unit you can learn more at

I have heard that there is a controversy about what type of smoke detector is best. Have you seen that there is any difference between detectors?

You are probably referring to a recent debate over the relative benefits of ionizing smoke detectors versus photoelectric models. Ionizing detectors are the least expensive, and therefore by far the most popular, representing approximately ninety percent of installed residential detectors. Ionizing detectors are very good at detecting the products of combustion produced by burning, or an actual open flame. Hence, they will very quickly let you know about the burning toast. Unfortunately, however, they are very poor at detecting smoke from cooler smoldering combustion, particularly from smoldering plastic products such as the foam in seat cushions or mattresses. Oftentimes, smoldering plastic products create large amounts of potentially deadly smoke before a flame or fire actually breaks out. Photoelectric smoke detectors are much more sensitive to visible smoke than the ionizing type of detector, and will alert an occupant much sooner to a low heat smoldering type of situation. On the other hand, photoelectric detectors are slower to detect fires that produce minimal amounts of smoke. Since seconds are important when trying to escape a fire, we would highly recommend that you have both types of detectors, or install combination units.

Despite all the public education we still find homes without any smoke detectors. It is critical that you have enough detectors and that they are placed in locations that will alert you when you are sleeping. Since eighty percent of deaths caused by residential fires occur at night, smoke detectors should be placed in common areas just outside of the bedrooms, at minimum. The best situation is to have integrated smoke detectors, with one on each floor and one in each bedroom. When one integrated detector goes off, they all sound the alarm. Alarm batteries should be replaced annually and smoke detectors should be replaced every 10 years. Hold a family fire drill, including operating the smoke detectors at night to see if they are capable of waking up the children. Make sure that they know what to do when the alarm goes off. And don’t forget to have at least one fully charged fire extinguisher on hand, and know how to use it.

I understand that we are required to have a carbon monoxide detector in the house when we sell. I placed the detector in the basement near the furnace, but have been told that this is incorrect. Where should it go?

In New York State the law requires that a carbon monoxide detector be installed, (under most circumstances,) in any single family or two family dwelling being sold. The proper location indicated by the law is the lowest level bedroom area. There are a couple of reasons for this. Carbon monoxide, or CO, is a byproduct of combustion. It is produced in lethal quantities when the combustion quality of a fossil fuel is poor, most commonly caused by distortion of the flame or an inadequate supply of oxygen, and when some of the resulting exhaust gases are entering the house rather than venting to the exterior. The source of CO is most commonly a malfunctioning gas fired appliance such as a furnace, boiler, or water heater, but could also include other fossil fuel appliances, such as coal or oil fired equipment. Other sources include wood burners, such as fireplaces, or gasoline engines such as a car idling in the garage or a gasoline generator. Given the wide variety of sources, a detector next to the furnace in the basement may not be exposed to the carbon monoxide coming from a source in another location. Secondly, since the most common occurrence of death from carbon monoxide is during sleep, we want to make sure the detector will wake you up if there is a problem. You probably won’t hear the detector when you most need the alarm if it is located in the basement.

Over our years in the inspection profession, we have been astounded at the frequency with which we have found conditions capable of introducing significant amounts of carbon monoxide into the homes we inspect. It takes just the right set of conditions for lethal quantities of carbon monoxide to poison unsuspecting occupants, but that combination has been perilously close many times. We urge our readers to install at least one carbon monoxide detector in their homes, whether they are selling or not.

I am selling my house, and my Realtor says that I am required to provide a carbon monoxide detector. I have an all-electric house, so why do I have to give the buyer a CO detector?

You have to provide the detector because the law says so. Since May of 2004 sellers of a one or two family dwellings in New York State are required to include a carbon monoxide (CO) detector with the house. (Tough luck for the people who live in three family or larger multiple dwellings, I guess.) According to the law, the detector should be installed in the lowest level bedroom area. It makes perfect sense to install a CO detector just outside of the bedrooms, because you are most vulnerable to carbon monoxide poisoning when asleep. The detector must be in a location where it will not be blocked by closed doors from detecting CO coming from another part of the house, and it should be placed in a location that will result in its being heard. From our perspective as safety oriented home inspectors, CO detectors should be installed outside of any bedroom at any level, and it would be a good idea to provide an extra unit in the basement utility area for even greater assurance.

Your question, of course, is based on the apparent lack of a source for any carbon monoxide in your house. While the primary source of potential carbon monoxide poisoning is combustion gases from natural gas appliances, there are several other potential sources that you may not have thought about. Any type of carbon based, or fossil fuel can produce carbon monoxide when burned. This means that the exhaust from your car in the attached garage could be a source, if you forget and leave it idling. The gasoline generator that you might use in the garage when the power goes out, could be dumping CO in the house, as well as the portable kerosene heater. If you have a fireplace, fumes from the embers of a dying fire are likely to include CO and could be drawn into the house by a poor draft. So, even if you don’t have gas heat, or any other gas appliances, carbon monoxide poisoning is not out of the question, and a good detector is cheap insurance.

I just bought a house with an in-ground swimming pool. I have never had one before and am very concerned because I have two small children. What safety measures should I be looking for?

You are right to be concerned about your children’s safety, as well as that of neighborhood children. Over 350 young children die due to drowning in swimming pools annually. There are many potential hazards associated with a pool, but ensuring the adequacy of the enclosure is probably the most important safety measure to address. By most codes the enclosure must be a minimum of four feet tall from the outside at all locations, including any gates. Gates must be self closing and self latching. Latch mechanism handles must be located on the pool side, or must be 54 inches above the ground on the outside. Any gaps between the gate and fence that would allow a child’s hand to reach the latch must be corrected. Fences must be designed to prevent any easy climbing from the exterior. Look for any gaps between the fence and the ground that might also allow entry. If the enclosure includes a wall of the house, any doors between the house and the pool should be self closing and latching per the rules for gates, or should be equipped with specially designed audible alarms. New rules adopted in New York State require new or significantly renovated pools to be equipped with an alarm that will detect a toddler falling into the water. These come in two types. One detects surface waves, the other sub-surface movement. The sub-surface type appears to be somewhat more reliable according to recent Consumer Product Safety Commission testing. Alarms designed to be worn by the child are also available but do not satisfy this requirement.

Electrical requirements near the pool should also be investigated. No electrical receptacles should be installed within ten feet of the pool, and any receptacles in the general pool area should be GFI type to prevent shock hazard. All metal pool equipment, including the pump, should be bonded together with heavy gauge copper wire. This should be visible at the pump motor. Have a licensed electrician inspect the pool wiring.

Finally, don’t forget simple vigilance. None of these safety features work if they are not activated or well maintained. And consider getting rid of any diving boards. They aren’t much of a hazard to the toddlers, but have been implicated in a lot of injuries and deaths among adults and teens.

I have a large tree near my house. I am concerned about the roots damaging the foundation and plan to have the tree removed. Should I have the roots removed also?

It is very rare in our climate, where foundation walls must extend deeper into the ground than the frost does, for tree roots to cause damage to foundations. Your home’s foundation offers no interest to the tree roots as they search for minerals and moisture. Trees can be very damaging to homes, but not generally to concrete or block foundation walls. Their roots do cause problems for walkways and any other structures that rest primarily on the surface of the ground, by causing heaving as they grow. Tree roots can also harbor termites which may begin to consume the nearby wood in the house as the colony grows. And tree roots often clog up older, poorly sealed sewer pipes as the roots search for the nutrients and moisture that the pipes convey.

The greater problem from trees is generally from the portion of tree that’s above ground. Older, and diseased or weakened trees often harbor extensive carpenter ants colonies. The ants start satellite colonies in the house as they forage for food. In addition to the obvious leaf and branch debris that clogs gutters and must be cleaned up from the yard, trees drop moisture and nutrients that feed damaging moss and lichen growth on roofs. Any tree limbs overhanging the house or located within 6 foot of the structure will also encourage squirrel entry. Squirrels can be incredibly destructive and should be absolutely excluded from our houses.

Most people love their trees. The cooling shade, bird habitat, and aesthetic advantages are undeniable, but their potential harm to homes is enormous. Keep any trees well away from the structure, look for any potential for damage to the house from falling limbs, and monitor their health closely. In your case, we would recommend having the roots ground down below the soil surface when the tree is removed just to reduce the likelihood that swarming termites will find the roots to be a commodious place to start a new nest.

We recently had a fire down the street from us, which got us wondering if you had any recommendations to reduce the risk of fires?

Let’s review some of the more obvious steps to take to ensure your safety before exploring the common causes of residential fires that we find as home inspectors. First, make sure that your smoke detectors are working, are in a location where they will be exposed to smoke from far flung areas of the home, and are located where you will be able to hear the alarm when sleeping. Second, make sure that you have an escape plan. If the common areas of the house are blocked off, can you and your family members escape directly from their bedrooms to the exterior? Bedrooms in attics or basements, or bedrooms with inadequately sized or located windows may be a problem to be resolved. Third, keep fire extinguishers handy, with one in the kitchen, one near any woodstove or fireplace, one in the garage, and one near the utility or laundry areas.

The next consideration should be to slow the spread of the fire. Fire resistant wall or ceiling finishes and self-closing fire doors, required in modern construction, should be installed between the garage and living space. Open chaseways from the basement or lower levels should be sealed off to prevent fires from spreading rapidly up through the home and into the attic. We can’t overemphasize the importance of sealing off the bottoms of any chaseways. Whether they’re being used for plumbing, chimneys, ducting, or laundry chutes, simple building materials can be used to keep them blocked, giving you more time to escape.

Electrical problems seem to be one of the most common sources of accidental fires. From our experience as home inspectors, this is not surprising. We constantly find electrical wiring in appallingly poor condition, and few houses are free of at least a few wiring deficiencies that could pose a shock or fire hazard. Poorly maintained heating and cooling equipment, and gas appliances, are commonly found, and are probably next on the list of fire sources. Hiring a home inspector to review the condition of the whole house and its major components, including the electrical system, heating system, and appliances, would be money well spent to keep your family safe.

The bricks toward the top of my chimney are loose and pieces are falling off. I had the chimney stuccoed a few years ago but this doesn’t seem to be holding. Is there any alternative to rebuilding the chimney?

There probably isn’t any good way to get around rebuilding the affected portion of your chimney. The masonry is likely to be too deteriorated to allow any sealer, such as stucco, to maintain a bond with the brick and mortar. It might be worth a try, but before you attempt to save the chimney we need to examine the cause for the deterioration. Chimneys are typically under tremendous stress from extreme heat, cold, chronic moisture, and exhaust gases, but especially from freezing. Bricks and mortar are generally porous. Since water expands when it turns to ice, moisture in the masonry literally blows the bricks apart in winter. The secret to chimney longevity is to keep the bricks and mortar as dry as possible. Assuming you have not installed a new furnace to an old chimney, the most likely source of excess moisture is rain water soaking in through the top of the chimney. The standard method for sealing the chimney top is for the mason to apply a mound of mortar around the projecting clay tile flue on top of the brick. This is economical for the mason, since he gets to use up his leftover mortar for this purpose when he is done laying the last brick. Unfortunately, mortar is not designed for this kind of exposure. Mortar is designed for good adhesion, flexibility, and workability when laying brick, rather than for durability. Mortar chimney “crowns” normally last only about 10 years before they crack and crumble, allowing water to seep into the brick. Instead, the chimney top should be sealed with a concrete crown. The concrete can be a pre-cast unit or can be cast in place. In either case, it is important that the concrete crown be wider than the dimensions of the chimney so that it will form a drip edge to keep rain water from washing down the sides of the chimney. With a proper concrete crown you may be able to keep the brickwork sufficiently dry to hold a stucco coating long enough to justify that approach to repair. Without a good concrete crown you’re just wasting your time and money.