Signs of a Mold
that you may have a potential mold problem in your home or
1. High Humidity
If you live in an area with high humidity,
then you should always be on the lookout for potential mold
problems. Naturally, the outdoor humidity affect indoor
humidity levels, creating a perfect environment for toxic mold
A relative humidity (RH) level of greater
than 55% promotes the growth of mold and other
fungi. (more about
relative humidity). Although relative humidity remains
fairly consistent outdoors, it fluctuates drastically
inside as a result of being altered by the artificial
heating and cooling (i.e. climate control by the HVAC
In which case, it is critical to closely
monitor the relative humidity level in various parts of your
home or building, since relative humidity can also vary
from room to room. (Relative
Humidity Sensor Buying Guide).
In addition to using humidity sensors to
monitor the moisture level, you can also run dehumidifiers and
employ other products and methods to control humidity in the
home or building.
Humidity in the Home
Humidity Sensor Buying Guide
to look for in a Dehumidifier
2. Water/Pipe Leaks
Mold needs moisture in order to grow and
thrive. Many mold problems originate as a result of some kind
of water intrusion, especially those that are not resolved
quickly. In which case, water and pipe leaks are common
culprits, since they provide plenty of moisture, and are often
undetected for days, months, or even years if minor enough.
When leaks are discovered, appropriate
steps are not normally taken to minimize potential mold growth problems
(Mold Problem Prevention Tips).
By the time they are discovered, it is often
too late, since the mold will have had ample opportunity to
grow in the same hard-to-find places where water leaks
occur, such as in wall cavities (Mold
Clean Up Tips).
Signs of a
Mold problems are very common after flooding
for obvious reasons (plenty of moisture which is conducive for
mold growth). Plus, it usually requires several days or weeks
to fully dry out the home or building once flooding occurs,
giving colonies of black mold more than adequate time to become
fully ingrained in these sections.
4. Mildewy/Musty Odors
Odors can often be the first or only sign
of a potential mold problem, since mold commonly propagates in
places not normally in view. This does not necessarily mean
that you definitely have a mold problem, but it should prompt
you to look for the other signs, or to look for the
mold growth itself (How to Find Mold).
In some cases, mildewy smells will only be
evident when the air conditioning or heat is turned on, or it
may just be much more evident when the HVAC system is
running. If this is the case, then it is very possible that
you have significant mold growth within the HVAC system.
5. Increased Allergy/Respiratory Symptoms
If one or more people living in a house, or
working in a building (especially if it is an unusually high
percentage of occupants) begin suffering allergic reactions
that seem to be associated with your home or building,
then it could be due to the presence of high levels of mold,
especially if other signs are also present.
This may mean that people began experiencing
much more allergic and respiratory-related symptoms after
moving into a home, or after beginning to work in a building.
Remember, that according to a 1999 Mayo
Clinic study, nearly all chronic sinus infections
(afflicting about 37 million Americans) are a result of mold.
Health Effects of
6. Signs of Toxic Poisoning
and other fungi produce Volatile Organic Compounds (VOCs)
during the process of degrading substances to obtain
VOCs are the cause of the typical “moldy/musty” commonly
associated with fungal contamination indoors.
Exposure to high levels of VOCs may irritate the mucous
membranes and the central nervous system leading to symptoms
of headaches, decreased attention span, difficulty
in concentration, and dizziness.
Health Effects of
7. Leaky Roof
Like other types of water leaks, water
intrusion through the roof is difficult to find until it is
too late. If you suspect a leaky roof, check in the attic
for signs of water damage or mold growth. Also be on the
lookout for signs of water damage or mold growth in ceilings
on the uppermost floor of the home.
8. Use of Humidifiers without Relative Humidity Control
Using humidifiers can easily raise the
moisture level in the air to the point where mold is
able to grow at a rapid rate. When using a humidifier, the
key is to regulate the relative humidity level, to ensure it stays
within 55-60% RH.
This can be accomplished with a relative
humidity sensor. However, if you are using a humidifier, it is
best to have one that can be programmed to automatically
shut off when relative humidity reaches 60%, such
as the SuperAire
humidifier (with built in relative humidity
sensors) by HumidifiersDirect.com.
9. Damp Basements or Crawl Spaces
Basements and crawl spaces tend to receive less
ventilation (especially crawl spaces), while also seeing cooler
temperatures. With all things being equal, cooler
temperatures will lead to a higher relative humidity
percentage, since cooler air is able to hold less water before
condensation occurs. Of course condensation means
In addition to all of this, basements and
crawl spaces are more likely to be neglected than other
parts of the home, so mold can grow undeterred for a longer
period of time.
Also, water from leaks in the home
will eventually make its way down to the lowest areas,
thanks to gravity.
Mold in Basements/Crawl Spaces
Preventing Mold Problems in
10. Condensation or Rusting
Condensation on or around pipes, windows, or
walls is a sign of a leak or high humidity. Rusting on pipes
in particular, and anything else metal, is also a sign of a
high humidity problem or nearby leak.
11. Lots of House Plants
House plants require consistent watering,
which increases moisture levels inside.
12. Discoloration of Walls (Water Stains)
Yellowish stains on walls and
ceilings are a sign of excessive moisture. In more obvious
cases, where mold growth may already be in full swing, the
wall or ceiling may have a greenish, brownish,
or blackish discoloration to it.
You may also notice places where the paint
is coming off due to moisture, or where it is
One way to check for mold growth is to move
a medical grade, flourescent tube ("black light")
around walls, ceilings, and even carpets while it is dark. A yellow
glow is a sign of mold growth.
Excessive Moisture in Walls
13. Cracked, Peeling Paint
This usually means that there is moisture
build up behind the paint. By the time the paint shows these
signs, the moisture has often had an opportunity to spawn the
growth of mold within the wall.
14. Blocked Gutters
Gutters that are blocked can cause water to
seep into walls, through the roof, and can cause water to
collect at the base of the foundation, which will result in
further water damage in the home or building.
15. Warped Wood
Naturally, moisture is going to cause wood
to warp. If wooden materials in your home have been
infiltrated by enough water to actually warp, then sufficient
levels of moisture are probably present to accelerate mold
16. Black Growth in Bathroom Tiles
Bathrooms are a favorite breeding ground of
mold. The increased moisture and common presence of tile
in bathrooms are each highly conducive to the proliferation of
Tile grout is porous and will
allow water penetration, and behind the tiles
themselves. In addition, dirt and other grime (favorite
foods of mold) are easily trapped in the grout. This
combination creates an ideal environment for mold to
Even if some type of sealant is applied,
tiles expand and contract, and pieces of grout will eventually
break off, compromising the seal. (preventing mold growth
17. Loosening of Drywall Tape
This is a sure sign that moisture has
infiltrated the wall.
18. Visible Biological/Mold Growth
This may seem like an obvious sign, but many
people do not take a little visible mold growth very
seriously. However, this can be an indication of a much larger
mold growth in less visible places.
Mold can take on a variety of appearances,
such as black, grey-brown, grey-green, white & orange
spots, or even pink or purple
splotches if growing behind vinyl wallpaper. Stachybotrys
is commonly a dark, slimy, greenish-black mold.
Some of the more common locations
where mold is found inside includes in bathroom tile,
basements/crawl spaces, and other damp and/or dark areas.
How you know if
what you've found is Mold
19. Clothes Dryers/Other Appliances Not Vented Outdoors
If the steam from these types of appliances
is vented inside, then this significant amount of additional
moisture creates a great environment for mold to flourish.
20. Poor Ventilation
If the air pressure in your home is
"negative", meaning the air pressure outside is
greater than it is inside, then it will force moisture and
contaminates back into the home. If the air pressure is well
into the "positive" side, then it can cause moisture
to be forced into walls. The air pressure in your home should
be slightly positive, or at least balanced.
21. Presence of Wet Materials Indoors
This can include rags, steam from cooking, indoor clothes
lines, carpet, or furniture. If these or other items are damp
for extended periods of time, then the moisture level can be
high enough to accommodate mold growth.
22. Mold Test
There are a variety of sampling techniques
that can be used to help determine whether or not you have
excessive levels of mold. There are mold tests that take samples
from the air, and some that take samples from surfaces.
Each method has its advantages and disadvantages.
Mold tests by themselves cannot give you
the full picture, but when combined with other evaluation
methods (such as those listed on this page) you can better
determine the extent of the problem.
Since they can be expensive, and usually
tell you only what you already know, it is usually best to
find the source of excessive moisture and to try fixing it
before resorting to a mold test.
Some techniques identify what species of
molds are present. This can be helpful since some mold species
pose a greater health risk than others.
(Mold Test Review)
All in all, you are generally better off
tracking relative humidity, since a relative humidity level of
55% or greater usually means that you will have indoor mold
Humidity Sensor Buying Guide).
If the signs point to a mold problem, then
the next step is to Find the Mold
Growth, so it can be cleaned and removed.
You should also start employing methods to Prevent
further Mold Growth (prevent it as much as humanly
How to Find Mold
- Where to look and ways to uncover mold growth in your
home or building.