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Indoor stains in buildings traced to black or dark thermal tracking or ghosting lines:
Building Air Leaks & Heat Loss Points. This article describes & diagnoses the cause of various interior wall and ceiling stains and explains how to recognize thermal tracking, (also called ghosting or ghosting stains or thermal bridging stains),
building air leaks, and building insulation defects.
Often these stains are mistaken for toxic indoor mold.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
What are Thermal Tracking, Ghosting, Sooting, Thermophoresis, Electrostatic Deposition, Plating-Out Stains
Ghosting Marks: what causes those dark stains on building interior walls & ceilings? Photos & text identify thermal tracking, thermal bridging, air bypass leaks, insulation defects and air movement in buildings.
Thermal tracking stains or dark thermal ghosting stains (also called thermal telegraphing stains) indoors indicate building air movement, air leaks, and points of heat loss which increase home heating or cooling cost.
Here we explain how to recognize poorly insulated building walls or ceilings and how to pinpoint building air leaks.
We provide a photo-guide to common indoor ceiling and wall stains and what they mean.
Why & how thermal tracking and ghosting stains could indicate very dangerous carbon monoxide hazards in a building.
Soot from natural gas, LP gas, or oil burners - sooting gas appliances are dangerous.
Thermal tracking marks can indicate thermal bridging: locations of building heat loss. We include this definition of THERMOPHORESIS
That makes some areas on an indoor surface slightly more damp than others.
As air moves by natural convection through the building, it typically flows up walls and across ceilings.
Airborne debris in the air, particularly soot such as that left by airborne house dust, by a heating system that needs service or by burning
candles (scented candles may be more of an IAQ issue), or by cigarette smoking, adheres more to the damp surfaces than to others, leaving black marks or "tracks."
Black thermal tracking stains may appear on interior walls and ceilings, not just on cool exterior building walls. It is also possible that an interior partition wall may be conducting heat out of the building through convective loop heat losses as well.
See CONVECTIVE LOOPS & THERMAL BYPASS LEAKS.
While most people don't use the terms thermal tracking or ghosting with great precision, it is useful to understand how particular stain patterns are laid down in a building. Understanding the location, shape, size, and intensity of a stain on a building wall or ceiling can help us understand how a building works, its energy efficiency, and the quality of its indoor air.
To track down and fix thermal tracking stains you will need to fix air leaks and provide insulation where it's missing or inadequate.
However beware that on occasion the leaks and moisture in a building that contribute to thermal tracking may have created a mold problem somewhere else than in the black thermal tracking or soot marks you see on walls and ceilings.
Because some clients have on occasion sent
samples to our mold test lab that really should not have been collected, much
less looked-at, we recommend that you review the photographs in these articles to see if the black stains you see are something other than mold.
When investigating a building for a mold problem, you can save mold test costs by learning
how to recognize Stuff that is Not Mold or is only Harmless Mold but may be mistaken for more serious contamination
- save your money
Eight Interacting Factors Determine When & Where Stains Appear in buildings
[Click to enlarge any image]
Thermal tracking or "ghosting" is the deposition of house dust and debris onto walls and ceilings in patterns caused by a combination of air movement, interior moisture, and in some cases, a source of high levels of particles.
The rate of particle deposition that ultimately forms these dark indoor stains depends on several variables including the following factors that I list alphabetically rather than in importance for the typical homeowner. I include links to related articles that go into greater depth but I suggest wading through this one in its entirety first.
Conflicting variables are at work in the deposition of soot and debris on building surfaces. Here are some examples:
More dust where more air moves: Building surfaces exposed to more air movement are exposed to more airborne dust and debris - so may become stained.
This phenomenon is most apparent where house dust and debris are deposited on and around air return registers in buildings. Where the air filtration system is not effective or the duct system is dirty, dust and debris are also deposited on and around warm or cool air supply registers. (This dust is most often harmless house dust comprised mostly of skin cells and fabric fibers.)
Less dust where more air moves: Building surfaces exposed to more air movement might, however, also be kept warmer and more dry due to that same movement, so the same areas may become less stained than their neighbors.
This phenomenon is most apparent in a building closet, or on a wall behind a picture or behind drapes, because less air moves over those surfaces, leaving the surface cooler, exposing the surface to higher moisture condensation, and thus causing more house dust (or soot) deposition than in other areas.
Let's look briefly at thermal tracking's causes, arranged alphabetically rather than in order of impact on the formation of indoor stains on ceilings & walls, or thermal tracking / ghosting:
Eight Factors that Determine the Level of Thermal Tracking or Dust Particle Deposition on Ceilings & Walls
Air velocity: the speed of air movement over a building surface affects the rate of deposition of particles on the surface. Faster air movement brings more particles in contact with the surface where depending on other factors, they may plate out or stick.
Air movement in buildings occurs at different velocities in different areas even within the same room, depending on the location of incoming air sources (such as an air conditioning or warm air heating vent) and on sources of heat that cause convection currents in the room or even inside building exterior walls or interior partition walls. This variation may explain why we see dark thermal tracking stains above heating radiators and baseboards even though those are not forced-air heating systems.
See AIR VELOCITY & MOVEMENT PATTERNS in this article (below) for details about this factor
Carbon Dioxide CO2 level: in public buildings or offices or your well-attended church or synagogue where the number of occupants might increase the indoor CO2 near 2000 ppm, increased carbon dioxide levels combined with high indoor moisture can encourage the deposit of white deposits of calcium bicarbonate.
This is a particular concern in museums or at the Sistine Chapel, as Grabon (2015) explains, noting that for the Sistene Chapel the HVAC system has been designed to keep the CO2 below 800ppm. You won't see these deposits in a normal residential structure.
Ceiling or Wall temperature: the interior surface temperature and its variation from the temperature of room air determines if condensation will occur on those surfaces at all.
Warm air carrying moisture will increase condensation on the cooler surfaces. If you can keep the wall surface temperature always 18F or 10C above the dew point temperature, there will be no condensation on your walls. You can do this by managing room temperature or by managing the RH of the air in the room, or both.
Dew point temperature: when the ceiling or wall surface temperature is below the dew point temperature moisture will condense on the surface.
The moisture collecting on those surfaces then causes more airborne particles to adhere. Keeping a wall temperature close to the nearby air temperature minimizes particle deposition. The dew point temperature is the air temperature at which the air is saturated: it can't hold any more water.
We exlore define dew point temperature and relative humidity (RH) and we explain the relationship of temperature and RH in a separate article at DEW POINT CALCULATION for WALLS
Non-Particulate airborne pollutants: other non-particulate pollutants also affect building surfaces, particularly sulfur dioxide (SO2), as in interiors where the RH is high, the moisture in air combining with SO2 can actually form sulphuric acid that in a museum or where there are frescoes or other important surfaces, the acid may attack these materials.
Particle composition & level in the air: soot, burning candles, fireplaces, pets, increase the particle level. In public buildings particles also enter the building from people, not just their pets, but also on shoes, clothing, carried items.
For protected areas such as museums and indoor frescoes, Grabon (2015) cites an HVAC design level that keeps the indoor dust concentrations (particle size range ParticulateMatter PM 2.5 microns) below 0.003 µg/ft3 (0.1 µg/m3). That's a dust control level enormously more stringent than you'd seek for a normal residential space.
For example the US EPA's 24-hour fine particulate standard is 35.0 µg/m3 - the same particle level as the output air from some of the best carpet vacuums cited by the Carpet and Rug Institute (CRI).
Rh as a Factor in the Development of Indoor Stains on Building Surfaces: If indoor humidity is excessive (say regularly over 50 or 55% RH) we may be encouraging both staining from soot and house-dust deposition as well as mold growth in a building.
Also we may be inviting excessive levels of dust mite activity which in turn increases the level of allergens in the building.
That is because higher humidity indoors provides more moisture to condense on cooler building surfaces whenever the temperature of a building surface reaches the dew point.
Stated another way, if a building has low indoor humidity, the amount of moisture available to condense on cool surfaces is less, so the rate of thermal tracking or soot deposition on those surfaces is less - at least due to this factor.
Wall surface temperature and its variation from the temperature of room air: warm air carrying moisture will increase condensation on the cooler surfaces.
If you can keep the wall surface temperature always 18F or 10C above the dew point temperature, there will be no condensation on your walls. You can do this by managing room temperature or by managing the RH of the air in the room, or both.
Even if the building humidity levels are low, high levels of indoor dust and debris can still lead to indoor stains and thermal tracking marks. Other factors that may be at play include electrostatic attraction or thermophoresis, discussed later in this article.
Air Velocity & Patterns vs the Level of Thermal Tracking or Dust Particle Deposition on Ceilings & Walls
Air velocity & air movement patterns: the speed of air movement over a building surface affects the rate of deposition of particles on the surface. Faster air movement brings more particles in contact with the surface where depending on other factors, they may plate out or stick.
Air movement in buildings occurs at different velocities in different areas even within the same room, depending on the location of incoming air sources (such as an air conditioning or warm air heating vent) and on sources of heat that cause convection currents in the room or even inside building exterior walls or interior partition walls.
This variation may explain why we see dark thermal tracking stains above heating radiators and baseboards even though those are not forced-air heating systems.
Air Movement Patterns as Factors in the Development of Indoor Stains on Building Surfaces
Specific and non-uniform moment of building air can lead to uneven soot or house dust deposition on building surfaces, and thus will cause stains and dark areas that are non-uniform . Surfaces across which more building air moves are exposed to a greater volume of air and thus a greater volume of dust particles.
Electrostatic deposition,plating out and thermophoresis of ultra-fine airborne particulate debris also explains black stains, sooting, or ghosting, as has been pointed out by Roger Hankey and Joe Lstiburek and others.
Electrostatic deposition refers to the sticking of particles to a surface due to a difference in electrical charge between the particle and the surface.
We often observe heavy electrostatic deposition of indoor dust and debris on building walls, ceilings, and other surfaces (most visibly on walls and ceilings) in homes where an ion generator is being used in the belief that it is "purifying" indoor air.
A friend in Rhinebeck, NY cranked up her indoor air ionizer to reduce the level of dog dust in her home - she boards as many as 15 dogs at a time in her home.
Indeed over just a few months we observed empirically that there was an increase in the rate of sooting on indoor painted walls and ceilings. Particles were probably sticking to other surfaces as well, but they were less visible.
Watch out: excessive use of indoor air ionizers, especially improperly adjusted, can produce harmful levels of ozone indoors.
Brownian motion, or pedesis, describes the random movement of particles, in this case airborne particles, perhaps impelled by energy from heat, light, or ambient air current, possibly plating out by impact collision with building surfaces.
But unlike common thermal tracking, particles that are deposited on building surfaces by electrostatic deposition, brownian motion, or thermophoresis may be expected to occur without the presence of uneven surface moisture, temperature, and thus classic thermal tracking features.
are likely to be more uniform in the areas they cover than particles deposited by thermal tracking
will not specifically map building wall studs, nails, or other cooler or more moist building surfaces
Filtration and Thermal Tracking or Ghosting on Carpeting and Possibly other Fabrics such as wall curtains can indeed explain dark stains on carpeting under doors and at room perimeters where there may be air leaks.
Lstiburek offers a compelling explanation that airborne dust and debris (of all particle sizes) is filtered out by the carpeting or other fabric surface over which air may be passing.
So a difference in air pressure between rooms (someone is running an exhaust fan for example), or air leaks at the perimeter of a floor (construction is leaky and cold air is rising from a crawl area or from outdoors into the occupied space of an upper floor,for example) indeed can deposit dark black stains on carpeting.
Airborne Particle Composition in Black Stains Found in Thermal Tracking or Electrostatic Deposition
Our photo of black vertical stripes on walls of a home was contributed by an InspectApedia reader who asked what they were. Because the lines so neatly map wall stud spacing these are almost certainly thermal tracking or ghosting marks explained in this article.
But what makes up the dark stains? Pretty much regardless of the variouis mechanisms that cause airborne particles to deposit on ceiligns or walls where they form dark stains or "sooting" or "ghosting" on interior building surfaces, the actual particles that can be expected to make up the stain include the following:
Soot and combustion products produced most often by cigarette smoking (brown wall stains), candles, especially scented candles or incense, soot from poorly-maintained oil fired heating appliances, soot from improperly-operating (and dangerous) gas-fired heating appliances, smoke particles from fireplaces or other indoor combustion activities (burning food on the stove?).
Particulates from pyrolysis in buildings: Lstiburek opines that pyrolysis of lint in clothes dryers and similar activities may also produce ultra-fine particles plating out on walls as soot or ash. Indeed, pyrolysis is a chemical process that through exposure to heat causes organic material decomposition that in turn lowers the combustion point of a material.
And as pyrolysis changes the properties of a material it can indeed release gases, liquids (tar) and char (solid residue) that could be deposited on building surfaces. just below.
Thermophoresis might be a factor in the development of indoor stains: when condensation occurs on a building surface at any level that makes that area more damp (and thus sticker) than its neighbors, the temperature and humidity-related particle deposition described above is almost certainly occurring in any building, and will be more noticeable in a building with high levels of airborne particulates and dust.
IAQ consultant Steven Temes, an industrial hygienist and microbial consultant points out,
ultrafine carbonaceous particles (such as candle soot) also accumulate on the colder surfaces due to a little known physical phenomenon called thermophoresis. This has to do with the driving force of the particle motion being its kinetic energy (when not overwhelmed by air currents) and the movement of the particle toward the cold surface, where it "plates out", adhering to the surface.
If the particle has an electrical charge (such as in a home where ozone generators or negative ion generators are in use) this plating-out process will be significantly increased. If you are using an ozone generator as an "air purifier" indoors, be sure to
see OZONE AIR PURIFIER WARNINGS
Other very fine airborne dirt or soil particles such as soil particles, organic particles, enter the building on animals, people, objects and airborne from nearby processes such as construction, incinerators, even simple vehicle traffic. Soot from diesel engines of some buses or other vehicles is a significant airborne particle source in many cities.
Skin cells from building occupants (humans, other animals) will almost certainly be present, as these are a common ingredient in house dust
Fabric fibers, in very small fragments may be present as these too are a common ingredient in house dust
What particles are unlikely to make up the black stains associated with thermal tracking or ghosting?
In our forensic lab we have examined surface particles from literally thousands of building samples, including soot stains from dark or dirty surfaces, leading to the opinion about thermal tracking and plating particle makeup.
Other indoor particles that may be common in buildings and are cited by some other writers including some building scientists (Lstiburek) are less likely to be found in the black or dark indoor surface stains we describe here, for the reasons we list below. Some of these less-likely sometimes-airborne particles that have been posed as candidates for participating in the thermal tracking or ghosting festival include:
Concrete dust: too heavy, does not remain airborne over long periods, typically gray or white
"Dirt" needs to be defined. Generic "dirt" formed of soil particles or road dust and debris are found at low levels in indoor air samples and are normally too heavy to remain airborne or appear in thermal tracking on walls and ceilings. Dirt will, of course, be present at high levels in carpeting.
Dirt as black smudges on walls may deposited by thermal tracking or by humans or animals in the building - the diagnosis of which black stain or dirt deposition source is at fault: creatures vs. airborne housedust lies in the deposition pattern.
Drywall (gypsum board) or plaster dust: these particles are typically white or gray and are easily identified in the microscope. They do not normally look gray or black on building surfaces.
"Gas smoke" - this is an undefined material; burning LP or natural gas produces carbon dioxide and water vapor, both colorless.
Watch out: If LP or natural gas fuel are producing visible smoke (or black soot) a very dangerous condition exists risking fatal carbon monoxide poisoning - shut off the equipment and consult an expert immediately; if smoke alarms or carbon monoxide alarms are sounding, leave the building.
"Insulation smoke" - is also an undefined term. Fiberglass and similar building insulation particles are rarely found on walls and ceilings in dark stained areas, though insulation particles are regularly found in indoor air and on horizontal surfaces in settled dust. Insulation fragments are too large to be part of the thermal tracking deposition process and are not black.
Lint, properly referred to as fabric fibers, is rarely found in thermal tracking stains (too large, heavy) but is very common in indoor horizontal surface dust.
However very fine lint particles, even without pyrolysis, may join other housedust particles to be deposited on building walls due to the thermal tracking process we describe here.
Mold: mold spores can include particles down around the 1micron level (though most are larger). While we find mold growth on indoor surfaces where there have been leaks or other mold-conducive conditions, we do not normally find high levels of mold spores in surface samples from vertical surfaces (walls) or overhead ceilings in buildings that are not themselves already mold contaminated.
Mold growth on walls may also follow moisture gradients and variations, but typically not in the same pattern and certainly not in the same texture as thermal tracking of dust and soot.
Brownian motion? As building scientist Joe Lstiburek points out, brownian motion also can cause particle adhesion to indoor building surfaces by the simple mechanism of mechanical impact of the particle with a building surface.
But particles that remain airborne in Brownian motion are ultra small and thus less likely to include most of the particles listed above.
Visual Inspection by an Expert can Usually Sort Out the Causes of Building Stains
Conceptually, the deposition of dust, soot, or debris on building surfaces out of moving air in buildings (as opposed to caused by animals or people touching surfaces) is a complex linear equation that is weighing different and conflicting factors.
Luckily, the visual inspection of the stained areas, combined with inspection of the building for moisture problems, insulation and ventilation problems, or for soot and debris sources, can normally identify the dominant effect and can with confidence conclude the cause and thus suggest the cure for these stains.
Why does Thermal Tracking or Ghosting Often Appear in Streaks or Lines?
Typically these dark lines mark the cooler wall or ceiling surface areas where studs or joists are present; you may also see dark spots in lines marking drywall nails or screws for the same reason.
In a conventionally-framed
wood structure, wall and ceiling framing is typically spaced on 16" or 24" centers, and thermal tracking will tend to cause
dust or soot to adhere to the interior surfaces at these locations. You can see this phenomenon in our ceiling stain photo (left).
Thermal tracking stains may appear at the top of the wall and extend onto the ceiling surface such as shown in this photograph.
These ceiling stains probably mark the location of ceiling joists (where the in-room ceiling surface temperature was kept a bit cooler since these locations
in the ceiling cavity are occupied by a wood joist rather than by insulation).
More Indoor Stains Identified as Ghosting or Bridging
A careful examination of the location of indoor stains permits the observer to use thermal tracking or soot marks on building walls or ceilings as an indicator of possible excessive (seasonal) interior moisture or other potential indoor air quality concerns.
Dark stains on building interior walls may appear in other patterns and could be from other causes - we provide photographs, description, diagnosis, and advice for many of these
indoor stains in this article series. Let's start with another example of THERMAL TRACKING BRIDGING GHOSTING so that we an distinguish these stains from others listed below.
pictures from our living room.
... these stains are getting worse ... my husband does notice that insulation seems to need work.... Everyone keeps saying it cant be healthy ... I'm worried
- K.C. 4/4/2014
Reply: how to recognize thermal tracking or ghosting stains in buildings
There is no doubt that we are looking at thermal tracking or "ghosting" - deposits of dust and soot on cooler, more humid areas of ceilings in your home.
These are not themselves a particular health concern but the conditions that cause thermal tracking, if they involve high indoor moisture levels, particularly if that moisture comes from a damp or wet basement or crawl space, could be a subtle clue that there is a hidden mold problem in the building.
Watch out: if the building soot source that is providing material for the black ghosting stains in your photos were an improperly-operating heating system or gas fired appliance dangerous conditions could be present such as carbon monoxide.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
ASHRAE resource on dew point and wall condensation - see the ASHRAE Fundamentals Handbook, available in many libraries. The following three ASHRAE Handbooks are also available at the InspectAPedia bookstore in the third page of our Insulate-Ventilate section:
2005 ASHRAE Handbook : Fundamentals: Inch-Pound Edition (2005 ASHRAE HANDBOOK : Fundamentals : I-P Edition) (Hardcover), Thomas H. Kuehn (Contributor), R. J. Couvillion (Contributor), John W. Coleman (Contributor), Narasipur Suryanarayana (Contributor), Zahid Ayub (Contributor), Robert Parsons (Author), ISBN-10: 1931862702 or ISBN-13: 978-1931862707
2004 ASHRAE Handbook : Heating, Ventilating, and Air-Conditioning: Systems and Equipment : Inch-Pound Edition (2004 ASHRAE Handbook : HVAC Systems and Equipment : I-P Edition) (Hardcover)
by American Society of Heating, ISBN-10: 1931862478 or ISBN-13: 978-1931862479
"2004 ASHRAE Handbook - HVAC Systems and Equipment The 2004 ASHRAE HandbookHVAC Systems and Equipment discusses various common systems and the equipment (components or assemblies) that comprise them, and describes features and differences. This information helps system designers and operators in selecting and using equipment. Major sections include Air-Conditioning and Heating Systems (chapters on system analysis and selection, air distribution, in-room terminal systems, centralized and decentralized systems, heat pumps, panel heating and cooling, cogeneration and engine-driven systems, heat recovery, steam and hydronic systems, district systems, small forced-air systems, infrared radiant heating, and water heating); Air-Handling Equipment (chapters on duct construction, air distribution, fans, coils, evaporative air-coolers, humidifiers, mechanical and desiccant dehumidification, air cleaners, industrial gas cleaning and air pollution control); Heating Equipment (chapters on automatic fuel-burning equipment, boilers, furnaces, in-space heaters, chimneys and flue vent systems, unit heaters, makeup air units, radiators, and solar equipment); General Components (chapters on compressors, condensers, cooling towers, liquid coolers, liquid-chilling systems, centrifugal pumps, motors and drives, pipes and fittings, valves, heat exchangers, and energy recovery equipment); and Unitary Equipment (chapters on air conditioners and heat pumps, room air conditioners and packaged terminal equipment, and a new chapter on mechanical dehumidifiers and heat pipes)."
1996 Ashrae Handbook Heating, Ventilating, and Air-Conditioning Systems and Equipment: Inch-Pound Edition (Hardcover), ISBN-10: 1883413346 or ISBN-13: 978-1883413347 ,
"The 1996 HVAC Systems and Equipment Handbook is the result of ASHRAE's continuing effort to update, expand and reorganize the Handbook Series. Over a third of the book has been revised and augmented with new chapters on hydronic heating and cooling systems design; fans; unit ventilator; unit heaters; and makeup air units. Extensive changes have been added to chapters on panel heating and cooling; cogeneration systems and engine and turbine drives; applied heat pump and heat recovery systems; humidifiers; desiccant dehumidification and pressure drying equipment, air-heating coils; chimney, gas vent, fireplace systems; cooling towers; centrifugal pumps; and air-to-air energy recovery. Separate I-P and SI editions."
Energy Savers: Whole House Systems Approach to Energy Efficient Home Design [copy on file as /interiors/Whole_House_Energy_Efficiency_DOE.pdf ] - U.S. Department of Energy
"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
Grabon, Michel, Jackie Anderson, Peter Bushnell, Aritz Calvo, and William Chadwick. "The Sistine Chapel: New HVAC System for Cultural Preservation." ASHRAE Journal 57, no. 6 (2015): 20.
Abstract: This article provides a review of the new HVAC and environmental control system designed
to preserve the majestic frescoes of the Sistine Chapel. The frescoes that decorate the
Chapel’s walls and ceiling faced increasing environmental challenges as a result of a
dramatic rise in visitors. When the original HVAC system was installed over 20 years ago,
it was designed to accommodate 700 visitors at a time; today there are up to 2,000. Critical
factors in the design of HVAC systems for museums and buildings with historic artifacts
include air temperature, air humidity, air circulation, airborne pollutants and sound level.
Lioy, Paul J., Thomas Wainman, Junfeng Zhang, and Susan Goldsmith. "Typical household vacuum cleaners: the collection efficiency and emissions characteristics for fine particles." Journal of the Air & Waste Management Association 49, no. 2 (1999): 200-206.
Abstract: The issue of fine particle (PM25) exposures and their potential health effects is a focus of scientific research because of the recently promulgated National Ambient Air Quality Standard for PM2 5. Before final implementation, the health and exposure basis for the standard will be reviewed by the U.S. Environmental Protection Agency within the next five years. As part of this process, it is necessary to understand total particle exposure issues and to determine the relative importance of the origin of PM2 5 exposure in various micro-environments. The results presented in this study examine emissions of fine particles from a previously uncharacterized indoor source: the residential vacuum cleaner. Eleven standard vacuum cleaners were tested for the emission rate of fine particles by their individual motors and for their efficiency in collecting laboratory-generated fine particles. An aerosol generator was used to introduce fine potassium chloride (KC1) particles into the vacuum cleaner inlet for the collection efficiency tests. Measurements of the motor emissions, which include carbon, and the KCl aerosol were made using a continuous HIAC/Royco 5130A light-scattering particle detector. All tests were conducted in a metal chamber specifically designed to completely contain the vacuum cleaner and operate it in a stationary position. For the tested vacuum cleaners, fine particle motor emissions ranged from 9.6 x 104 to 3.34 x 108 particles/min, which were estimated to be 0.028 to 176 mg/min for mass emissions, respectively. The vast majority of particles released were in the range of 0.3-0.5 mm in diameter. The lowest particle emission rate was obtained for a vacuum cleaner that had a high efficiency (HEPA) filter placed after the vacuum cleaner bag and the motor within a sealed exhaust system. This vacuum cleaner removed the KC1particles that escaped the vacuum cleaner bag and the particles emitted by the motor. Results obtained for the KC1 collection efficiency tests show >99% of the fine particles were captured by the two vacuum cleaners that used a HEPA filter. A series of tests conducted on two vacuum cleaners found that the motors also emitted ultra-fine particles above 0.01 mm in diameter at rates of greater than 108 ultra-fine particles/CF of air. The model that had the best collection efficiency for fine particles also reduced the ultra-fine particle emissions by a factor of 1 x 103.
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Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: email@example.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
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