Self-Assessment Guide for signs that a home may be affected by drywall
Associated Corrosion.
The Florida Department of Health developed this self-assessment guide to make
it easier for homeowners to determine if their home meets the criteria for a
possible case of drywall associated corrosion as specified in our current case definition. These evaluation steps
included here are designed to be taken by a homeowner or building trades
professional without any special training in materials analysis or environmental
sampling. These steps focus on the appearance of discoloration and corrosion of
metals consistent with the presence of reduced sulfur gasses. You must be able
answer yes to each indicator before you meet the possible case definition. To
reach an increased level of confidence that a home suffers from drywall
associated corrosion, we recommend materials analysis by trained professionals
as described in the case definition.
Indicator 1 – Age of Home
The problem of drywall associated corrosion is known to occur in homes built,
renovated or repaired with drywall replacement since 2001.
Assessment of indicator 1 (Yes/No)
Was the house built, renovated or repaired with drywall replacement during
the time period of concern?
Indicator 2 – Blackening corrosion of air conditioning evaporator coil or
repeated A/C evaporator coil failure
This corrosion can result in refrigerant leakage making it impossible to cool
the home requiring evaporator coil replacement. This type of corrosion is
characterized by the blackening of copper in and around the air handler unit.
Note that accessing the A/C coils may be dangerous, and should be performed by a
licensed A/C contractor. There are three ways to determine if your home meets
this indicator:
Option 1: Repeated A/C evaporator coil failure
Coil failures indicative of this corrosion problem typically occur every 6-14
months, instead of the normal 10 to 20 years. If the A/C evaporator coil has
been replaced, contact the repair company to see if they have any notes that
indicate the condition of the coil during replacement. Ask the repair company if
copper in the evaporator coil had turned black or were there signs of a
different coil failure mechanism.
Option 2: For air handling units located in an inside a mechanical closet or
in the garage.
Look to see if the compressed refrigerant line going into the air handler has
a black appearance, typical of sulfur corrosion. This copper line is
approximately ¼ inch in diameter and can be easily viewed without opening the
air handling unit (AHU) or removing any panels. If the air handler is in an
interior closet or in the garage, go to it and look at the un-insulated copper
line going into the air handler. Compare it to the images below. The image on
the left shows the normal copper color
which changes with age and normal exposure to the environment. The image on the
right shows the blackening copper corrosion that is typically caused by exposure
to corrosive sulfide gasses.
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version

Normal Copper Color |
Sulfide Corroded |
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Option 3: For air handlers in any location
It is less likely to find the blackened copper corrosion on the un-insulated
refrigerant line in homes with corrosive drywall when the air handler is located
in the attic or crawlspace. We recommend you have a state licensed air
conditioning contractor evaluate copper corrosion on the coils inside these
units. You may also have a a contractor evaluate the coils for copper corrosion
when the air handler is in a closet or garage.
All images below open in a new window and display a larger
version

Normal |
Sulfide Corroded |

Normal copper in a rusty steel frame

Normal copper tubing

Normal copper tubing
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Sulfide corroded coil
|
Assessment of indicator 2 (Yes/No)
Was blackening corrosion found on copper components of the air handler or
have there been multiple A/C evaporator replacements?
Indicator 3 – Observed metal corrosion
Electrical wiring as well as other copper, silver and metal fixtures may
exhibit sulfide corrosion when exposed to the reduced sulfur gases. Most of the
following items may be examined by the homeowner. Due to the electrical shock
hazard presented by live wires, we recommend you hire a licensed electrician to
inspect electrical system components.
- copper wires, ground wires, and electrical connectors
- un-insulated and un-coated copper pipes and fittings
- chrome-plated bathroom fixtures
- silver and copper jewelry
- mirror backing in bathrooms
Examples of Electrical wiring/system corrosion indicators
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version

Normal |
Corroded |

Normal wiring
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Black corrosion on wiring
|

Normal outlet
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Black corrosion on
wiring
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Examples of Copper Tubing and Fixtures
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version

Normal |
Corroded |

Normal copper plumbing
|

Corroded copper plumbing
|

Normal shut off valve
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Corroded shut off
valve
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For additional examples of metal corrosion, see the photos in the case definition.
Assessment of indicator 3 (Yes/No)
Did you find blackening or signs of sulfur like corrosion on one or more of
the listed items?
Final Analysis:
If you answered 'Yes' to all three of the previous questions, the home meets
our criteria for a possible case of drywall associated corrosion. Before
proceeding to remediate your home, we recommend you have your home evaluated by
a trained professional to see if your home meets case definition criteria 3 for
a confirmed case.
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