smoke or mold?

The home is a modular ranch built in 1985. Very heavy smokers. Well insulated attic with large gable and ridge vents and metal roof. The plywood sheething was black as shown. Could this be caused by excessive cigarette smoke? I question mold because of the good venting. The interior of the home was yellow with nicotine.

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That appears to be a vent from a bathroom or kitchen fan. My bet is bathroom. It also appears to be newer. My guess is the bathroom fan emptied into the attic in this location for years until the last sale/inspection when this was installed. Pretty small picture to really get a good look.


Moist air from the bathroom exhaust vent and a hot roof (metal likely not insulated well from the decking) kinda ‘scorched’ it mayhap?

used my magnifier and from what I see that is not from smoke.
My guess is the underlayment had a moisture problem from that vent not flashed properly.
Were u able to get a moisture reading?

Hot air full of moisture hits the underside of the cold (Vermont) roof. Moisture condenses and wood gets soaked. Microbial growth.

Decay fungi, moderate decay of roof sheathing. Sheathing has probably lost 35% strength, maybe more.

Good theory

Moisture maybe but the bath fan had been disconnected ans covered. The nails sticking into the roof sheeting were not rusted, signs of moisture. Didn’t take a moisture reading. Thanks to all for the good comments.

Looks like mold to me, probably a pen-asp or cladosporium.


Only one way to tell for sure, do a mold test. In this situation I would use a swab and send it to Pro-Lab. Results in 24Hrs.

It’s mold. Good venting does not ensure a dry attic!!!


From the above:
What To Do About a Wet Attic

The usual response is to increase attic ventilation. This is the wrong approach. In some cases, adding ventilation will actually pull more moist house air up into the attic and make the problem worse. The best way to fix a wet attic is to stop air movement, or leaks, from the house. Once this is done, the existing ventilation is usually more than enough to keep the attic dry.

And from a 1980’s article, *Attic Ventilation and Airsealing, * from the NY State Energy Research and Development Authority:

“In fact, there is no guarantee that providing a specified area of passive ventilation openings will yield some desired level of of ventilation”

I agree Brian. Ventilate all you want but without preventing heat loss and air movement … But for the original question; that is mold or other fungi untill proven otherwise.
Recommend “further evaluation by qualified specialist”.

Advise for mold testing to cover yourself.

Do you think you can make that pic any smaller?

Looks like moisture accumulation which caused the mold looking build-up.

Gable and ridge vent do not make good ventilation…air comes in the gable and out the ridge…nothing circulates down near the eave walls.

Still, it looks like evidence of condensation to me too.


I have seen this condition many, many times and it always turned out to be mold.

I STRONGLY recommend that you have a swab send to Pro Lab or another Bona Fide mold testing facility ASAP and certainly before closing.

  • **IF your client does not want this home tested for Mold then be SURE that you get a DISCLAIMER.

Good luck!

When we see the stuff, why do we have to test for it??? Are we supposed to make $$$$$ at every chance…even when not needed? Come on, get real about things!

Here’s what I see going on too much: **Scare the sh!t out of them; then pick their pockets!!! **

Saved a family about $8,000 (quote from the area’s largest engineering company) on a “mould cleanup” two summers ago. Gave them info so they could do it themselves- my charge $60…I was inspecting on the next street that day and spent 15-20 minutes on site. The “mould” problem was: (1) an attic that looked like the initial picture (no real need to clean that mould- just change the conditions to provide a dry sheathing year round; (2) less than 10 sq ft of dark mould in a basement corner; (3) a 1973 rotting softwood garage door (eng. co’s comments: Do not go into the garage- hazardous to your health.) The decay mould was white filamentous mycelia…very similar and maybe the same species as the decay fungus you see rotting dead spruce, pine, fir trees in the forest!!! Then I guess the corollary would be: DO NOT GO INTO THE FOREST- HAZARADOUS TO YOUR HEALTH. COME ON!!!

From America’s preimminent building scientist:

"If you see it or smell it, you do not have to test for it. It is more important to get rid of the mould ( or conditions) rather than spend a lot of money trying to find out more about it***.***" (by sampling and identifying the species of mould- our comment) Dr. Joe Lstiburek, P. Eng., Phd…; Building Scientist and principal at Building Science Corporation (Website:

Hello Mr. Jack:

Here is a thought on your question from a slightly different angle; that from a professional investigator.

In your question, you have already limited your answers. You have presumed, without any apparent reason, that the material on the surface must be either smoke or mould. Why? What if it is neither smoke or mould? Instead of asking “Is it smoke or mould?” shouldn’t you instead be asking “What is it?”

In 19 years of performing both mould inspections and smoke inspections (both criminal arson and civil liability investigations), I have never seen a single instance anywhere under any of the very strange circumstances I’m in where smoke has even slightly resembled mould or where mould has even slightly resembled smoke.

The two entities are so vastly different that their deposition, patterns, occurrence, visual aspects and even odors would allow an immediate on-site differentiation at a glance (without the collection of a single sample).

Some of your previous responders posted some lazy-brain responses “to cover yourself” and suggested taking mould samples. However, far from covering yourself, the suggested lazy-brain actions could result in even greater liability for you and provide a terrible disservice for your client. Here’s a simple example of how –

Let’s assume, for the moment, it is either exclusively smoke or mould. You follow a lazy choice and instead of investigating the discoloration properly, you simply collect the suggested swab and send it to the suggested laboratory, “Pro-Labs.” The result of the swab comes back positive (but then of course it would, even if there was no mould problem, the result would comeback positive), and Pro-Labs in their report interpret the data and report that the swab indicates that “Elevated Mold Condition Exists” (but then, as I have mentioned before, I have reviewed MANY Pro-Labs reports, wherein Pro-Labs has reported that the samples indicate that elevated mould conditions exist, where in fact, the property did NOT have ANY kind of elevated mould conditions ANYWHERE in the property).

So, now you have a lab report for a “mould test” that contains “data” that for all you know is exactly similar to a swab that one may take from virtually any attic, including one with no discoloration; and therefore, the report contains information that you cannot interpret. But, you tell your client the attic has a mould problem, since that is what the report says.

Consider for a moment what the US Centers for Disease Control says about such sampling (1):

The results of samples taken in your unique situation cannot be interpreted without physical inspection of the contaminated area or without considering the building’s characteristics and the factors that led to the present condition.

Ah, what the heck, what would they know? After all, as Mr. Gromiko would tell you, they’re not NACHI Home Inspectors, therefore, it’s criminal for them to provide instruction on mould inspections. Take a look at Messrs. Gromiko, and Porter recent comments on industrial hygienists, (of course, if you consider those comments, you are going to have to completely ignore the disclaimer found at the bottom of the page of the Pro-Labs report summary… ouch).

Also, you are going to have to explain to the homeowner why you similarly ignored the US Centers for Disease Control when they said:

Other than in a controlled, limited, research setting, sampling for biological agents in the environment cannot be meaningfully interpreted and would not significantly affect relevant decisions regarding remediation, reoccupancy, handling or disposal of waste and debris, worker protection or safety, or public health.

Aww, what the heck, Nick knows more than that bunch of egghead industrial hygienists at the CDC, right? And besides, you have been through the Pro-Labs one day class, so you’re every bit as much an expert as they are, right?

So you tell the homeowner that the deposition is mould, and the elevated mould conditions exist in the house.

Homeowner Smith: “What do I do?”

Mr. Jack: “Remediate the mould!”

So, the homeowner spends $15,000 to remediate the mould, and sells the house to the Jones family (with their two darling little girls).

But guess what? Yes of course there was mold on the surface – duh! That mould grew there thirty years ago when the building material was sitting out in the lumber yard, and became colonized with “Elevated Mould.” After which, it was installed into the house, and for the last 30 years the mould (now completely covered with smoke particles) can no longer be seen.

Mr. Jack: “Oooops… what was that? Smoke? Did you just say smoke? What do you mean smoke?”

Oh, didn’t I mention, the discoloration actually was smoke after all, and the smoke was coming from smoldering wires in the attic, that were shorting out, and smoldering the surround paper and other building materials. But then, see your “mould test” didn’t answer the necessary question “What is it?” In fact, your Pro-Labs mould test didn’t even answer the question you thought it did, which was “Is it mould or smoke?” Your Pro-Labs sample ONLY answered a single question “Is mould present on that surface at that location?” Which any fool could have told you that it was present, even an egghead industrial hygienist, without having to collect a sample.

Hey - But look at the bright side! The entire Jones family died in the subsequent fire three months later, so they will never know just how bloody wrong you were or how bloody incompetent you were or how foolish you were to follow the advice of the lazy-brains, instead of doing your job correctly.

And don’t worry about that attorney who is now trying to contact you, I’m sure he just represents the lottery board and is trying to tell you that you are the luckiest guy on earth – you hit the jack-pot!

Of, course, I just made all that up, and it is entirely an unreasonable scenario that could NEVER happen, right? By the way, would you like to see the photos of the Jones house and those darling little girls as found by the arson team and that will be entered as exhibits during the trial? I have some.

Just some thoughts, on the matter. Either way, it’s the same to me – except of course, I will make money off the lazy-brain course of action, when the Jones estate hires me to evaluate the mould inspection you performed. Ouch. I make rather a lot of money off the lazy-brains and their lazy-brain suggestions.

p.s. I wonder if you have ever actually read the disclaimer at the end of a Pro-Labs report. Hmmmm.

Caoimhín P. Connell
Forensic Industrial Hygienist
Forensic Applications, Inc.

  1. US Centers for Disease Control, Mold: General Information: Basic Facts | CDC APRHB, 2007

The opinions expressed here are exclusively my personal opinions and do not necessarily reflect my professional opinion, opinion of my employer, agency, peers, or professional affiliates. The above post is for information only and does not reflect professional advice and is not intended to supercede the professional advice of others.


A classic case!
As a mold certified dude, I see this “staining” very often.
The cause is most usually due to poor INTAKE ventilation.
Those of you who agreed that adding all the upper vents in the world would not help, are right. Stuff the lower soffit ends of the soffits and bang! you have a stale air sittuation.
Add to that, fans that vent in the attic space, lack of weatherstripping at the hatch, dark colored shingle/roofing, cool nights and you have a condusive condition for mold growth (a steady source of moisture).
In my experience in testing this “staining”, most time it turns out to be an aspergillis genus, never smoke (unless there was a fire or something, and it would be more evenly spread.)
When you see this in an attic, it will most likely be in corners, and at the lower end of the slope (soffit ends), and if it is blotchy or in patched areas. The recommendation is clearly to add INTAKE venting if you feel the OUT venting is OK. True that adding gable vents will NOT help at all, to have flow, focus on the soffit venting.

I thought I had balls!!
Good points though!