We all instinctively make a visual inspection of our environment for danger each day. We teach our children to watch out for cars when they cross the street, and we look where we step to avoid tripping over a garden hose. Looking for air quality indoors is not quite so instinctive, but with a little practice it will become second nature to you. Visual clues are everywhere: on the ceiling, on the wall, and inside the air system and ducts. With a combination of direct visual observations and remote viewing instruments, a remarkably accurate picture of a building's air quality can be drawn.

Conditions throughout the occupied and unoccupied spaces as well as exterior conditions affect the quality of the air within a building. The key to a meaningful IAQ investigation is the intelligent collection and interpretation of direct and remote visual clues. Of course, temperature and humidity readings, biological, gas (VOC) and particulate samples, as well as occupant interviews will be required to validate a theory based on visual observations. A thorough visual inspection will often reduce the number of samples required to obtain an accurate picture of the dynamics of the pollutant paths within a building saving time and costs to the client.

Where To Begin

Visual inspection by the unaided eye is where all IAQ investigations begin, whether we realize it or not. I find myself looking up and observe a new ceiling tile I begin to wonder why it was replaced. Was there a water stain? Was it a roof leak, a sewage overflow or a fire sprinkler pipe that was leaking for months prior to the replacement? Then I start to think of the consequences of each. But I am getting ahead of myself.

What do we mean by visual inspection? Well, there is DIRECT visual inspection such as the observation of one new ceiling tile. Then there is REMOTE or INDIRECT visual inspection, which can be done with a mirror and a flashlight to look around a corner into a duct or heat exchanger. To see around corners and deep into a duct or wall cavity a video camera with a variety of insertion techniques is required. Finally, there is ANALYTICAL visual inspection where you rely on building blue prints to get a clue to how the building's systems interact in a manner that may be detrimental to the air quality in the occupied area.

The simple direct observations are the most valuable at the beginning of an IAQ investigation. Are there a lot of portable fans around the office? Are there portable electric heaters under a lot of desks? This would indicate either inadequate heating or cooling in these areas by the building's air system. Perhaps the fans are to divert an unpleasant odor that is migrating into these areas.

Looking for water and evidence of water is very important. Mold spores are everywhere, and if there is moisture and a food source, such as dust or the cellulose backing on drywall, mold can begin to grow in as little as 24 hours. Look for tell-tale stains on the ceiling or around the baseboards. Recent repainting of only one wall or one new section of carpet are clues that water may have been there recently. Examine the Condensate pan carefully. If the pan is not level or the drain is plugged, water may be collecting in the internal insulation of the air handler.

The exterior of the building may offer clues to water infiltration. Walk around the exterior and look for evidence that sprinklers repeatedly wet the same area of the walls over and over. Is there a decorative pond or waterfall near the foundation of the building? Is there evidence of standing water on the roof due to inadequate drainage or cooling tower overflow? None of these conditions prove a problem, but they highlight areas where biological samples may need to be taken to verify or refute the presence of mold growth and bacteria.

What about air flow? How can you visually observe that? Are employees wearing sweaters in the summer? Are there pieces of cardboard taped in or on the diffusers? In both cases there will likely be some complaints about temperature in these areas. Do you see doors propped open with a chair? Does the trash bin in the loading dock have a lot of debris tailing off towards the doors or away from the building. This might give you a clue to building pressure and whether odors may be pulled into the building because of too much air being exhausted. Where are those fresh air intakes anyway? Near the exhaust hood from the restaurant? Just above the parking lot tollbooth where cars stop and idle all day long?

To find out some of these things, a look at the security camera tapes may be useful. Unfortunately, most security cameras are not aimed to gather data for the IAQ investigator, so it is useful to have your own video camera system to look inside the ducts, the ceiling plenum, under raised floors and even inside of wall spaces where water can be seeping for years before there are any visual indications on the outside wall surfaces.

At one time the mirror and flashlight were the only visual aids available to look inside of hard to reach areas of the air system, the plenum space, duct systems and even inside the furnace heat exchanger. The fiber optic borescope was a breakthrough. With just a half-inch hole you could insert a viewing device with a light source and get a 360-degree view of that area. The hole was relatively easy to patch. Since the viewing distance was limited, a lot of holes were often needed to observe the whole system and then need to be patched.

Borescopes were very expensive, had a short range (2 feet in a straight line, usually) and difficult to adapt to 35mm or video cameras. Though prices have come down, and some have been adapted directly to video cameras, the development of very small, inexpensive low light video cameras has taken over the remote viewing field in recent years.

Video Systems

The video camera with its own light source of LED's is rugged enough to take a lot of banging around in the air system. Some manufacturers of video systems even provide for a means to attach the camera to a cleaning brush shaft to direct the cleaning process by watching the monitor. How often have you wondered if your brush has reached the end of a run, or worse, you forced it through an unseen damper and couldn't get it out? Seeing the end of the duct or the damper would be very useful.

A video camera image can be displayed on a screen at the job site, but its real advantage is its ability to record the inspection on a normal VHS videotape. This tape can be played back for the commercial client, along with a post cleaning inspection recording of the same area. In many federal government jobs, "Before & After" documentation is a requirement.

In residential work, the video inspection will assists your air system evaluation of how much work is needed, but it will also provide a valuable educational tool to show the customer the conditions of their ducts. The tape can be left for other members of the family to evaluate after you have gone.

How do you get these video cameras into the ducts? The simplest method is to hold the camera in your hand and reach as far as possible. This is a high-tech approach to the mirror and flashlight and is, in my opinion, of limited value.

Semi-flexible rods can be used to push the camera in a straight duct and are particularly useful in a vertical riser. The rods are useful until you reach the first real turn.

The camera can be attached to a duct cleaning brush and ride in with the tool. This is useful in documenting the actual cleaning process and will allow intelligent maneuvering of the cleaning tool based on real time observations, but this does not assist with an inspection prior to performing the cleaning.

A stiff but flexible insertion cable on some camera systems allows penetration of 20 feet or more into a duct system. It takes some twisting and pushing to make it around some twists and turns, but since you are viewing the duct ahead of the camera, you can tell when to push and when to twist-and which way to twist. Most of a duct system can be viewed by entering through the supply ducts. Most duct runs are 25 feet or less, but for longer runs, a 1.5-inch to 2-inch access hole will need to be cut and patched. Wheels attached to the camera head can aid in the insertion process. With wheels attached, the camera must remain upright for the wheels to be of benefit, so a heavier "trolley" system will provide a more stable base. Inevitably, the camera will run over an uneven section of duct or some protruding screws or a tight turn in a flex duct that will tip over the camera. If the wheels are larger than the height of the camera head, they will continue to roll even though the image is upside down. It is an advantage to be able to remove the wheels to inspect smaller, tighter areas of the air system, so be sure the wheels are easily removable in the field. Bathroom and clothes dryer exhaust ducts are too small for most wheel systems.

For a long large duct system, a robot camera can be "driven" into a duct, turned from sided to side and some even have forward and rear view to observe the entry path as well as the exit. Some offer cleaning and coating tools that can attach to the motorized robot, as well. To provide all these features and to get sufficient traction, a robot has to be relatively large and heavy. A 12-inch round duct would be a challenge for many robots, and 12-inch flexible duct would be impossible. But if you are working on square duct over 12-inch wide, the robot camera has the potential for viewing unobstructed lengths of most any duct system, just beware of dampers, turn vaines and vertical drops.

Before you run out and buy one, be aware that this functionality comes at a substantial price, be prepared for sticker shock.

What You Can See

What do you expect to see with your camera that you cannot see by direct visual inspection? I have seen what appears to be a lake from underground water filling a 36-inch duct to a depth of 4-inch. This was a swamp or more accurately a whole ecosystem with stalactites hanging from the top of the duct around a corner where nobody suspected it. I have seen underground ducts that been distorted by the pressure of the earth and burst open to allow roots, dirt, and insects into the fresh air supply. In one public restroom exhaust system there was a coating of dust debris 4 inches thick on top, bottom and sides. The debris coating was on the entire length of the system and up to the roof, a total of 60 feet. What does that have to do with indoor air quality? The reduced exhaust airflow forced unpleasant odors into the adjoining restaurant. Collapsed, broken, water damaged ducts and stuck dampers are common, as well as the usual dirt, mold, water stains and leaks in the air system.

Sometimes a visual clue must be investigated further. When a pipe or rod was observed in a vertical duct above, but not serving a restroom, it led to a closer look. It was actually a handle to a 16-pound sledgehammer that had apparently been dropped by a workman during a remodeling project two stories above. The hammer had broken the end cap loose and allowed restroom odors to fill the vertical supply duct between run cycles. When the fan would run, the odors would be forced into the offices.

To summarize, keep your eyes and you mind open and look everywhere. If possible use a remote video camera to look around corners and farther than your eyes can see. When you think you know what the visual clues are telling you, take biological, VOC, and physical samples to validate your theories.

Mike Stanovich is the chief instructor for Phase I, IAQ Investigation classes at Air-Care's headquarters in Las Vegas, Nev., and performs air quality testing and designs video inspection equipment and air duct cleaning equipment. He is also certified by NADCA, and is a charter member of American Indoor Air Quality Council, Las Vegas Chapter. You can reach him by calling (702) 454-5515 or by e-mail at mstanovich@air-care.com.