Sick Building Syndrome: How to Know If Your Building Is Making You Sick

There's a term for that feeling when you walk into a building and something just feels... off.

Maybe it's a headache that shows up every afternoon at work and disappears on weekends. Maybe it's the sinus congestion that started when you moved into your new apartment and never went away. Maybe it's the brain fog that lifts every time you go on vacation.

It's called Sick Building Syndrome — and it affects tens of millions of people who have no idea their building is the problem.

I know, because I was one of them. My apartment looked perfectly normal. But it was slowly making me seriously ill. By the time I figured it out, I'd developed Chronic Inflammatory Response Syndrome (CIRS) and spent three years recovering.

That experience is why I built Moldmap — a platform where people can check buildings for mold risk and air quality before they move in. Because nobody should have to get sick to learn that buildings can be dangerous.

What Is Sick Building Syndrome?

Sick Building Syndrome (SBS) is a condition recognized by the World Health Organization (WHO) in which occupants of a building experience acute health symptoms that seem to be linked directly to time spent in the building. The symptoms improve or disappear completely when the person leaves.

The WHO has estimated that up to 30% of new and remodeled buildings may have indoor air quality problems serious enough to cause health complaints. That's not a fringe claim — that's the World Health Organization.

SBS is different from "Building-Related Illness" (BRI), where a specific cause can be identified (like Legionnaires' disease from a contaminated HVAC system). With SBS, the symptoms are real and consistent, but they often can't be traced to a single contaminant. Instead, it's usually a combination of factors working together.

The Most Common Symptoms

Sick Building Syndrome symptoms are frustratingly nonspecific — which is exactly why so many people dismiss them or attribute them to something else. Common symptoms include:

Respiratory

Stuffy or runny nose
Dry or irritated throat
Cough
Shortness of breath
Chest tightness
Worsening asthma symptoms

Neurological

Headaches
Difficulty concentrating
Fatigue and lethargy
Dizziness

Skin and Eyes

Dry, itchy, or irritated eyes
Skin rashes
Dry or irritated skin

General

Nausea
Muscle aches
General feeling of malaise — "I just don't feel right"

The key diagnostic pattern is this: symptoms appear or worsen when you're in the building, and they improve when you leave. If your headaches happen every day at the office but never on weekends, that's a signal. If your allergies started the month you moved into your apartment and nothing else changed, that's a signal.

What Causes Sick Building Syndrome?

SBS rarely has a single cause. It's usually a combination of factors, and different buildings have different problems. Here are the most common contributors:

1. Inadequate Ventilation

This is the #1 cause identified in SBS investigations. Modern buildings are designed to be energy-efficient, which often means they're sealed tight. That's great for your heating bill but terrible for air quality.

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommends a minimum of 15-20 cubic feet per minute (CFM) of outdoor air per person. Many buildings — especially older ones that have been "tightened up" for energy efficiency — fall well below this.

When fresh air can't get in, pollutants concentrate. CO2 levels rise. Humidity becomes harder to control. And the air you're breathing becomes increasingly stale and contaminated.

2. Mold and Microbial Growth

This is the big one — and it's the factor that hit me personally.

Anywhere there's moisture, there can be mold. Common moisture sources in buildings include:

Roof leaks
Plumbing leaks (especially slow, hidden ones)
Condensation on cold surfaces
Flooding history
High indoor humidity (above 60%)
HVAC systems with standing water in drain pans

Mold doesn't just cause allergic reactions. Certain molds produce mycotoxins — toxic compounds that can trigger serious inflammatory responses, especially in the roughly 25% of people with genetic susceptibility (the HLA gene variations associated with CIRS).

The EPA estimates that roughly 50% of buildings in the United States have some degree of water damage. That's a staggering number, and it means that mold exposure is far more common than most people realize.

3. Chemical Contaminants from Indoor Sources

Modern buildings are full of materials that release chemicals into the air:

Volatile Organic Compounds (VOCs) from paint, carpet, furniture, cleaning products, and office equipment
Formaldehyde from pressed wood products, insulation, and adhesives
Pesticides used in building maintenance
Fragrances from air fresheners, cleaning products, and personal care products used by other occupants

New buildings and recently renovated spaces are especially prone to high VOC levels — a phenomenon sometimes called "new building smell." It's not just an odor; it's a chemical exposure.

4. Chemical Contaminants from Outdoor Sources

Buildings near highways, parking garages, or industrial areas can pull in contaminated outdoor air through their ventilation systems:

Vehicle exhaust
Loading dock fumes
Dumpster area emissions
Nearby construction dust

If a building's air intake is poorly positioned — say, near a parking garage exhaust vent — occupants can be exposed to elevated levels of carbon monoxide, nitrogen dioxide, and particulate matter.

5. Temperature and Humidity Problems

Thermal comfort affects perception and health more than most people realize:

Too hot or too cold = increased stress, reduced concentration
Too humid (above 60%) = mold growth, dust mite proliferation, bacterial growth
Too dry (below 30%) = respiratory irritation, dry eyes, increased susceptibility to infections

The sweet spot is 40-50% relative humidity with temperature between 68-76°F. But maintaining this consistently across a large building is genuinely difficult, and many buildings don't manage it well.

6. Electromagnetic and Lighting Issues

These are less commonly discussed but can contribute:

Poor lighting — insufficient natural light, flickering fluorescents, and harsh artificial lighting can cause headaches, eye strain, and fatigue
Noise — constant HVAC noise, office equipment, and poor acoustic design increase stress and reduce concentration

Buildings Most at Risk

Some buildings are more likely to cause SBS than others:

Buildings constructed or renovated in the 1970s-1990s — the peak era of "tight building" energy efficiency, often with inadequate ventilation design
Buildings with flat roofs — more prone to ponding water and roof leaks
Buildings with a history of water damage — even if the damage was "fixed," mold can persist behind walls
Buildings with deferred maintenance — HVAC systems that aren't regularly serviced, filters that aren't changed, drain pans that aren't cleaned
Ground-floor and basement units — more exposure to soil moisture, groundwater, and flooding
Buildings near bodies of water — higher ambient humidity
Hotels — high occupancy turnover, variable housekeeping quality, industrial HVAC systems that may not be well-maintained

How to Investigate Your Own Building

If you suspect your building might be making you sick, here's a systematic approach:

Step 1: Track Your Symptoms

Before doing anything else, keep a simple log for two weeks:

What symptoms do you experience?
When do they start and stop?
Do they improve on weekends, vacations, or when you're away from the building?
Do other occupants report similar symptoms?

This pattern data is your most powerful diagnostic tool.

Step 2: Check the Basics

Do a walkthrough of your space and common areas. Look for:

Water stains on ceilings, walls, or around windows
Musty or unusual odors — especially in bathrooms, basements, and near HVAC vents
Visible mold — check window frames, bathroom grout, under sinks, around air vents
Condensation on windows (indicates excess humidity)
HVAC vents — dark discoloration around supply vents can indicate mold in the ductwork

Step 3: Measure What You Can

Some basic measurements you can do yourself:

Humidity — a $15 hygrometer from Amazon can tell you if your indoor humidity is in the safe range (30-50%). Consistently above 60% is a problem.
CO2 — portable CO2 monitors ($50-100) can reveal ventilation adequacy. Indoor CO2 above 1,000 ppm suggests insufficient fresh air.
Temperature — note variations across rooms and times of day.

Step 4: Check the Building's History

This is where Moldmap comes in. Search for your building to see:

Community reviews mentioning mold, air quality, or health issues
Mold risk scores based on aggregated data
Photos and documentation from other tenants or guests

You can also check public records for code violations, flood history, and complaint records.

Step 5: Consider Professional Testing

If your symptom tracking and basic investigation suggest a problem, professional testing can provide definitive answers:

Indoor Air Quality (IAQ) assessment — measures particulates, VOCs, CO2, humidity, temperature, and airflow
Mold testing — ERMI (Environmental Relative Moldiness Index), air sampling, or surface sampling
HVAC inspection — checking ductwork, drain pans, filters, and coil cleanliness

Cost varies, but a basic IAQ assessment typically runs $300-$800. ERMI testing is usually $200-$400 for the kit plus lab analysis.

What You Can Do Right Now

Whether you're in a building that's making you sick or just want to protect yourself going forward:

If You're Currently Affected

Document everything. Photos, symptom logs, dates. This matters if you need to break a lease or request remediation.
Improve your immediate air quality. A portable HEPA air purifier in your bedroom can significantly reduce particulate and mold spore exposure. It's not a cure, but it helps.
Notify your landlord or building management in writing. Email is best — you want a paper trail. Be specific about your symptoms and what you've observed.
Know your rights. Most states have habitability laws that require landlords to maintain safe living conditions. Mold and air quality issues often fall under these protections.
See a doctor. Specifically, find a practitioner who understands environmental illness and CIRS. Standard doctors may dismiss your symptoms.

If You're Looking for a New Place

Search on Moldmap before you sign a lease or book a hotel. Check for mold risk data and community reviews.
Do the walk-through inspection described above during every showing.
Ask direct questions about water damage history, ventilation systems, and maintenance schedules.
Trust your nose and your gut. If a space doesn't feel right, it probably isn't.

For Everyone

Share your experience. If you've lived or worked in a building with air quality issues, leave a review on Moldmap. Your data point could prevent someone else from getting sick.
Talk about it. Sick Building Syndrome affects millions of people, but most of them don't know that's what's happening. The more we normalize talking about indoor air quality, the faster things change.

Why This Matters More Than Ever

We spend approximately 90% of our lives indoors. Yet indoor air quality is almost completely unregulated for residential buildings. There's no requirement for landlords to test air quality. No standard disclosure about water damage history. No rating system for the healthiness of the air you'll breathe every day.

That's what we're building at Moldmap — a trust layer for indoor air. A way for communities to share their experiences and protect each other. A world where you can check the air quality of a building as easily as you can check its Yelp reviews.

We're not there yet. But every review, every check-in, every person who takes indoor air quality seriously brings us closer.

Your building shouldn't make you sick. And if it does, you deserve to know about it before you sign.

-justin

Moldmap is the world's first community-powered healthy indoor air platform. Search 126,000+ apartments, hotels, and rentals for mold risk scores and indoor air quality reviews at moldmap.io.

This article is for informational purposes only and does not constitute medical advice. If you suspect your building is making you sick, please consult a healthcare professional experienced in environmental medicine.