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  1. #1
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    Default Black air filter

    Any ideas on why this air filter would turn black within a week. The air handler was recently inspected by a licensed AC and given the thumbs up. The coils are a little damaged but were not dirty. FYI - this is in a first floor condominium. There was / is a problem with the tub leaking upstairs. Instead of correcting the problem, they just stopped using the tub. There has been no recent construction or any open areas where dust could come in. All of the walls and ceilings were checked with both a thermal imaging camera and moisture meter and everything came up dry. There is a cat and a dog in the home but there were no hairs on the filter or coils. There is no gas in the unit. The water heater is electric and located under the air handler.

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    Bill Siegel
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  2. #2
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    Default Re: Black air filter

    Smokers, candles, lousy cook, fireplace, other sources of black particulate matter (soot) from a furnace or water heater?

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

  3. #3
    John Arnold's Avatar
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    Default Re: Black air filter

    Any signs of candle use?

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
    www.ArnoldHomeInspections.com

  4. #4
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    Default Re: Black air filter

    Could there be an open return air somewhere sucking air into the heating unit from between the walls?

    Raymond Wand Home Inspection Service
    http://www.raymondwand.ca
    The value of experience is not in seeing much, but in seeing wisely.

  5. #5
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    Default Re: Black air filter

    The candles is an interesting theory. There were candles on the wall, but they were about 10-12 feet from the air filter. I do not know if there were any closer. Those candles did leave marks on the wall and ceiling.

    The return is through the closet door, and just for info, the total run of the air ducts is not more than 8 feet in any direction.

    Bill Siegel
    Florida Home Inspection Team Inc.

  6. #6
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    Default Re: Black air filter

    Candles are likely the cause given the soot on the walls. They must burn them quite a bit!

    Raymond Wand Home Inspection Service
    http://www.raymondwand.ca
    The value of experience is not in seeing much, but in seeing wisely.

  7. #7
    Jerry Peck's Avatar
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    Default Re: Black air filter

    What did the filter behind it look like?

    Typically, when a filter gets dirty, there is dirt along the sides of the cardboard frame and that is stark black/white difference, almost as though the filter media had charcoal content and was black to start with.

    Just too dang clean all the way around that black part with nada on the white part.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  8. #8
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    Default Re: Black air filter

    The filter was black on the back side also. The two filters you see on the floor were exactly the same - both had turned black in 4-6 days. There was a new filter in the air handler. It was white and looked normal.

    Bill Siegel
    Florida Home Inspection Team Inc.

  9. #9
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    Default Re: Black air filter

    Candles. If you see soot plating out on the walls and ceilings, just imagine the amount the filters will see when the blower is running.

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

  10. #10
    Bob Harper's Avatar
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    Exclamation Re: Black particulate

    As a consultant who investigates Black Particulate Matter cases, I can assure you all it takes is ONE candle to trash a home. However, there are a lot of other sources so you cannot assume.

    You won't know for sure the black stuff is indeed 'soot' without proper lab testing. Whatever the BPM is, you can be sure there is alot more of it all over the home. One expensive mess to clean up. The house should be inspected by one knowledgeable in these matters (usually Not an HVAC tech), samples analyzed,which will guide remediation, then the place thoroughly cleaned. With the source identified, you can then take steps to ensure it does not repeat.

    Let me know if you need my assistance.
    Bob

    Keep the fire in the fireplace.

  11. #11
    A.D. Miller's Avatar
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    Default Re: Black particulate

    As a consultant who investigates Black Particulate Matter cases, I can assure you all it takes is ONE candle to trash a home.
    BH: Do not take this to heart, but the above statement sounds a lot like hyperbole.

    Google "black particulate matter" to find almost nothing on the subject. The reason is, in my opinion, that this is a mightily embroidered way of saying soot, or black carbon.

    Of course, I am often wrong. Show me the error in my reasoning.


  12. #12
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    Default Re: Black particulate

    Quote Originally Posted by A.D. Miller View Post
    BH: Do not take this to heart, but the above statement sounds a lot like hyperbole.

    Google "black particulate matter" to find almost nothing on the subject. The reason is, in my opinion, that this is a mightily embroidered way of saying soot, or black carbon.

    Of course, I am often wrong. Show me the error in my reasoning.
    ADM: Did you google "black particulate matter" WITH the quotes? I did, and got quite a few hits.

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
    www.ArnoldHomeInspections.com

  13. #13
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    Default Re: Black air filter

    Is the condo in a high traffic area?

    Still think there is an open return air duct drawing air from areas other than through return grills.

    I'd be inclined to seal the return ducts and run the heating system and see what the output side flow is like.

    Raymond Wand Home Inspection Service
    http://www.raymondwand.ca
    The value of experience is not in seeing much, but in seeing wisely.

  14. #14
    Jerry Peck's Avatar
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    Default Re: Black air filter

    Bill,

    First I would try one of these filters ( 3M Filtrete Ultra Allergen Filter ).

    I doubt they will get black within a week.

    I have been using these (the Ultra Allergen ones) for about 6 years or so and they start out white and gradually "get dirty looking" - but not black.

    I still think that black is too perfectly on ONLY the filter media and not ANY on the white frame around the media. I don't know of any filter which fits that exactly into the air opening what no air hits the surrounding frame and the surrounding frame does not get anything on it.

    Not much cost to try that and I'm guessing it does not get black - meaning it is a filter media aspect and not an air aspect.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  15. #15
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    Default Re: Black particulate

    Quote Originally Posted by Bob Harper View Post
    As a consultant who investigates Black Particulate Matter cases, I can assure you all it takes is ONE candle to trash a home. However, there are a lot of other sources so you cannot assume.

    You won't know for sure the black stuff is indeed 'soot' without proper lab testing. Whatever the BPM is, you can be sure there is alot more of it all over the home. One expensive mess to clean up. The house should be inspected by one knowledgeable in these matters (usually Not an HVAC tech), samples analyzed,which will guide remediation, then the place thoroughly cleaned. With the source identified, you can then take steps to ensure it does not repeat.

    Let me know if you need my assistance.
    Bob
    Bob do you have a standard statement for my reports on this issue ?

    Best

    Ron


  16. #16
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    Default Re: Black air filter

    Could be candles, but in just a few days? If it was caused by candles in that short period of time, I would think that the condo would smell like a big candle. Look for the candles in the jars, they produce more soot due to their higher oil content.

    I have seen similar conditions when the homeowner used an ozone machine to make the air smell clean. The ozone makes the particulates plate-out and the air filters just collect the particulates which are coal black in color.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  17. #17
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    Cool BPM?

    Aaron, not a problem---I get that all the time, esp. from professionals. BPM used to be called Black Carbon, Black Soot or similar terms until testing began revealing it wasn't always carbonaceous soot based. I have posted at length on this site several times so before I repeat, please do a little searching. I will leave you with the notion the 'stuff' you see can be a variety of things and often is a combination such as aerolized long chain aliphatic hydrocarbons, dust, mold, dirt, insulation particles to even tiny chunks of food. Even if it is hydrocarbon based, you would need to distinguish btw a gaseous fuel versus a solid or liquid based fuel to determine the probable source and thus guide remediation.

    Ron, sorry I don't have something canned for you. If you read my posts, I'm sure you can cook up something for now. I'll see what I can do.

    JP, be careful with high MERV filters--the HVAC guys love them............because they cause so much restriction they burn up the blower motors! They can also whack out the delta T and combustion efficiency. I'll try to get Davidr to comment on that aspect. Just remember the primary function of a filter is to protect the A coil---not your lungs and ANY change to the ducts including duct sealing has a cause and effect.

    Raymond, I agree with duct sealing. In fact, it's in the codes now. However, since it makes a change to the system, it should be followed up by combustion analysis.

    Scott, yes, I've seen ONE jar candle trash a home in just a day or two. When they get down near the bottom of the jar, there is very little O2 getting in, retention of CO2, which displaces the O2, exhaust fume turbulence and incomplete combustion causing much higher production of soot and unburned aerosolized fuel. These particulates act like fly paper to collect other particulates (reported pets in the home) and yes, you can have the creeping crud manifest very quickly. BTW, what you are seeing is only the tip of the iceberg. See Jim Luttral's comments about plating out, which is correct. There are other predictable points of deposition and these are determined by the type of particulate and the mechanism of delivery.

    Could have been someone just changing the vacuum sweeper bag right in front of a return, too. You just never know.

    Keep in mind filters are not gasketed and, in fact as we all sadly know, most fit rather sloppily in the rack. That means you have blow-by so next stop is the blower, then HX, then A coil, ducts, then your lungs and house surfaces. Cleaning/ replacing just the filter doesn't make all that stuff just disappear. It must be mechanically removed/ cleaned= expensive.

    FYI, most insurance companies will pay for this remediation then try to subrogate against the suspected offender.

    HTH,
    Bob

    Keep the fire in the fireplace.

  18. #18
    Jerry Peck's Avatar
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    Default Re: BPM?

    Quote Originally Posted by Bob Harper View Post
    JP, be careful with high MERV filters--the HVAC guys love them............because they cause so much restriction they burn up the blower motors! They can also whack out the delta T
    That would actually help the TD by slowing the air flow down, air spending more time over the coil would raise the TD.

    and combustion efficiency.
    That I have no idea about.

    I'll try to get Davidr to comment on that aspect.
    Thanks, that would be great.

    Just remember the primary function of a filter is to protect the A coil---not your lungs and ANY change to the ducts including duct sealing has a cause and effect.
    Yep, that I agree with and know.

    As I said, I've been using them about 6 years (maybe even longer) and have had no problem with the equipment, and in fact they keep the coil cleaner (that IS the intended purpose, is it not ). And by keeping the coil cleaner ... it also keeps the air cleaner.

    In South Florida, we replaced the a/c system in 1996 with a 14.6 SEER unit (high end at that time), started using those filters probably around 2002 or so (not sure) and had no problems on that system after using them, kept everything cleaner too.

    Up here, the a/c system is from 1995, we bought the house in 2006 and have been using them since then with no problems on the units.

    Had an a/c technician replace the capacitor when it went bad last month and he checked the system and said it was operating better than almost any he has seen of that age, and cleaner too (and we have not had the coil cleaned since we bought it and have no idea when it was cleaned before that, if ever).

    While those filters DO restrict the air flow per "square inch of return opening size", the pleating effect of the filters offers a much greater "square inch filter size", reducing, if not eliminating, the restriction effect.

    Those Ultra filters are like the car engine filters, serious pleating for significantly increased fitter area size, allowing for more dense filters to filter out finer particles yet allow for increased breathing of the engines / a/c system.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
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  19. #19
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    Default Re: BPM?

    Quote Originally Posted by Jerry Peck View Post

    While those filters DO restrict the air flow per "square inch of return opening size", the pleating effect of the filters offers a much greater "square inch filter size", reducing, if not eliminating, the restriction effect.

    Those Ultra filters are like the car engine filters, serious pleating for significantly increased fitter area size, allowing for more dense filters to filter out finer particles yet allow for increased breathing of the engines / a/c system.
    This is what we have been led to believe but they don't work like that unfortunately.
    I've had to eat a lot of humble pie on these things as in the past I recommended them only to find they were sending fans off their performance curves.

    These filters can work and work well but you have to increase the surface area to almost double that of what a fiberglass filter would be to maintain a lower face velocity across the media itself.
    If this isn't done and the media is restrictive it can actually makes things worse due to issues like filter bypass (particulate bypassing the filter) being amplified.

    The thicker filters can have a lower pressure drop but depending on the manufacturer of the media I have seen them be just as bad as the 1" pleated.

    When you start slowing the airflow down across a heat exchanger it will make the delta T increase which depending on what it is can cause undue stress on the heat exchanger and connections themselves.
    Combustion stack temperatures fluctuate on a bell curve, if the airflow is right the temperatures will be dead on if it is off the stack temperatures will go up due to ineffective heat transfer.
    These filters if not allowed for can send the flue gas temperatures in a properly operating system off that bell curve.

    They have an additional side effect also, they increase return side duct leakage downstream of the filter.
    If you had a fiberglass filter that wasn't very restrictive this might not be an issue.
    If you replace it with a pleated model it can increase the cabinet leakage on a gas furnace enough to make a water heater backdraft.

    Like Bob said all kinds of cause and effect type stuff going on.

    Measured Performance more than just a buzzword

  20. #20
    ray jackson's Avatar
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    Default Re: Black air filter

    I recently had this same issue at a customers place. I had heard about it in a training class. the instructor said that the black was from VOC's (Volatile Organic Compounds). Look it up. Carbon is actually vented from different materials in the home.


  21. #21
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    Default Re: Black air filter

    Years ago (30 to be exact in our first home), we had an air filter do this same thing cause my better half decided to clean out the ashes in the fireplace with a vacuum cleaner. Not realizing that the vacuum cleaner bag would not trap the fine particles of the ashes, it became air bourne and the return air sucked in the particles causing the filter to turn black.

    It was a mess to clean up.

    rick


  22. #22
    Ted Menelly's Avatar
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    Default Re: Black air filter

    As far as the pleated filters go. I have used them since they came out eons ago. I have put them in every system of every home I have lived in (many). I have to say that I never had a problem with any of the systems. I was warned from the beginning that that would harm the system ion some way (blower motor, duct leakage as Bob mentioned.

    Never a problem and the dust in the home is diminished to the extreme compared to the spun fiberglass useless filters that only catch big dust bunnies. Every service I had was always the smae comment about the opration of the units and their cleanliness. I am sure there have been some blower motors somewhere that have had to have been replaced. Maybe it was the blower motor with the problem.

    Ted Menelly, Castle Home Inspection Services
    www.inspectmycastle.com
    Fort Worth, Keller, Southlake, Plano, Flower Mound, DFW, TX

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