Indoor Environmental Professional - Know How and When to Use One

Christine Daecher, DO
Nov 19
3 min read

If you or a family member has become ill from living or working in a water-damaged building, you know how frustrating and overwhelming the process can be—both in identifying the presence of mold and bacteria and in figuring out how to address it.

Take a moment to look at the photos. Before reading the captions, see if you can identify the issues that could lead to a water-damaged building.

Educate Yourself About Water-Damaged Buildings

Learning the basics will help you make informed decisions. There are many excellent online resources, but one of the first I recommend is Dr. Shoemaker’s House Hunting Guide, which he sells on his website for about $7 (link below).

A note of caution: while the guide is extremely helpful, it is written with homes in the Northeast and Midwest in mind—areas where basements are common. Homes in the Southeastern U.S. face different challenges, especially related to humidity.

Start With Your Own Testing

Before bringing in a professional, I strongly recommend that homeowners start with their own objective testing for water-damaged buildings. The two primary options are:

HERTSMI-2
ERMI

These PCR-based dust tests go beyond surface-level inspections. They detect and identify fungal DNA, including hyphal fragments, which provides a much clearer and more accurate picture of what is present in the environment.

If your home has two HVAC zones, you should collect two separate tests.

Completing your own initial testing offers key advantages:

It gives you a baseline to compare against professional results.
It helps confirm whether the building is likely safe or problematic.
It arms you with knowledge so you’re less vulnerable to being sold unnecessary services.

I will link to my detailed post on testing for water-damaged buildings at the end of this article.

Humidity Matters—Especially in the Southeast

In the Southeast, the real issue isn’t just heat—it’s humidity. At around 70% humidity, moisture condenses on your skin, making you feel sticky. Building materials act the same way: they absorb moisture, which can create ideal conditions for mold growth.

In contrast, the arid Southwest can exceed 100°F without high humidity, which changes how buildings behave and where moisture problems appear.

This is why choosing a professional familiar with your regional climate is critical.

When to Bring in a Professional Mold Assessor

After completing your own testing—or if you’ve already discovered significant water damage—the next step is to hire a mold assessor.

A few important points:

The assessor should not be the same person who performs remediation.
Ideally, look for someone who follows the standards of the American Council of Accredited Certification (ACAC):
ACAC has a clear rule:An assessor cannot perform both assessment and remediation for the same client within the same year. This avoids conflicts of interest.

Some states, including Florida and Texas, require mold assessors to be licensed. Licensing creates clearer separation between assessment and remediation.

This is important because remediators often lack training in microbiology or in identifying likely areas of hidden growth. A truly independent assessor protects you from unnecessary or incomplete remediation recommendations.

Many Problems Can Be Identified From HERTSMI-2 or ERMI Alone

A skilled assessor can often give meaningful advice directly from your dust test results. This reduces unnecessary additional testing and saves you money.

Again, choose someone familiar with your climate region, because building design and moisture behavior differ dramatically between the Southeast, Northeast, Midwest, and Southwest.

Common Mistakes in Mold Testing

Outside of not following the instructions from the lab, here are some of the common errors people make when collecting samples:

1. Using inadequate tests

Air sampling and use of petri dishes that sit for a few days is not the way to test your home for water damage.

2. Not testing large or separate spaces individually

A large atrium or great room should be tested separately, as airflow and particle distribution differ. Each HVAC zone should be tested separately to help pinpoint any problems. If a particular room has concerning visible mold, it should be tested separately.

3. Not getting enough dust; the house is too clean

Unfortunately, some of us keep the house "too clean" to produce an adequate dust sample. This is your time to hold off on dusting for several weeks to let dust accumulate.

4. Taking Poor Outdoor Comparison Samples

Less commonly, you may choose to sample the outdoor mold species native to your area to see how the results compare to what is in the home. When comparing indoor species to outdoor species, you need a proper outdoor control. Do not sample from a porch, deck, or rusty railing. Instead, collect the sample at a mailbox or street sign, at least 20 feet away from the home.