Understanding Negative Air Pressure and CO Risk: What Happened in Osceola Could Happen Anywhere

On Friday, September 12, 2025, students and staff at Clarke Middle/High School campus in Osceola, Iowa had to evacuate their building after carbon monoxide sensors detected levels of carbon monoxide (CO). After investigation, officials determined that "negative air pressure" was the culprit behind the carbon monoxide buildup.

If you're like most people, you probably read that explanation and thought, "What exactly does that mean?" As a mom whose two boys survived carbon monoxide poisoning at their daycare, and who has spent years advocating for better CO protection in schools, I want to break this down in terms we can all understand. Because what happened in Osceola isn't a fluke. It's a growing risk in schools across the country, and every parent and educator needs to understand why.

What Is Negative Air Pressure? (And Why Should You Care?)

Think of your school building as if it's breathing. Air needs to move in and out naturally. Negative air pressure occurs when more air is being pulled out of a building than is being drawn in. It's like the building is holding its breath, creating a vacuum effect that sucks air from wherever it can find it.

Now here's the dangerous part: when a building is "hungry" for air due to negative pressure, it doesn't just pull in nice, clean air from outside. It can pull air from places you definitely don't want it to come from. Like:

• Boiler rooms and mechanical spaces where the school's heating equipment operates

• Storage areas, basements, or lower levels where maintenance equipment is housed

• Areas around the school's chimney stacks and HVAC exhaust points

• Loading docks or service areas where delivery trucks might be idling

• Even from neighboring buildings or parking structures with running vehicles

When combustion appliances (furnaces, boilers, water heaters) are running, they produce carbon monoxide as a normal byproduct. Under normal conditions, this CO gets safely vented outside. But when negative air pressure takes over, it can actually pull those deadly gases back into the building instead of letting them escape.

Here's the critical point: You don't even need a fuel-burning appliance inside the school for this to happen. If there's a boiler room, furnace, or even a neighboring building with combustion appliances, negative air pressure can pull CO from those sources into occupied spaces.

Why This Problem Is Getting Worse (And Why Older Buildings Aren't Safe Either)

You've probably heard schools and other buildings described as more "energy efficient" and "tightly sealed" than they used to be. That sounds good, right? We want to save energy and keep heating and cooling costs down.

But here's what nobody talks about: when buildings become more airtight, the air inside has fewer places to go. Modern construction techniques, better windows, improved insulation, and energy-saving measures have made our schools much more sealed than buildings constructed decades ago.

Here's the thing though—older school buildings face this problem too, just for different reasons. Many of our school campuses were built decades ago when nobody was thinking about air pressure balance. Over the years, these older buildings have been retrofitted with:

• More powerful exhaust fans in cafeterias and gymnasiums

• Updated HVAC systems that weren't designed for the original building layout

• New bathroom ventilation systems

• Kitchen equipment with heavy-duty exhaust requirements

• Sealed windows and doors as part of "improvement" projects

The result? An older building that was never designed to handle modern ventilation demands, creating negative pressure conditions that the original architects never anticipated.

In the old days, buildings were naturally "leaky." Air moved in and out through small gaps and cracks, maintaining a more natural balance. But even those older buildings lose their natural "breathability" when we add powerful modern exhaust systems without adding adequate makeup air systems to compensate.

Add to this the fact that many schools are running on tight budgets with aging, mismatched HVAC components. Sometimes exhaust fans are more powerful than the systems bringing fresh air in. Sometimes building modifications are made without considering how they'll affect air pressure. Whether your child attends a brand-new energy-efficient school or a decades-old campus, negative air pressure conditions can turn deadly.

The Detection Gap That's Putting Kids at Risk

Now let's talk about something that keeps me up at night: how schools detect carbon monoxide.

Many schools—especially smaller districts or older facilities—still rely on single-station CO alarms. These are the battery-operated or plug-in units you might have in your home. While these alarms can save lives, they have limitations in large buildings like schools:

Location matters tremendously. A single CO alarm in a hallway might not detect dangerous levels building up in a classroom on the other side of the building. Carbon monoxide can accumulate in pockets, especially in buildings with complex air flow patterns.

Time delays can be dangerous. Single-station alarms only sound when CO reaches dangerous levels right where that alarm is located. In a large building, by the time one alarm goes off, students and staff in other areas may have already been exposed to dangerous levels for extended periods.

They don't provide building-wide coverage. Unlike connected detection systems that monitor multiple points throughout a building and can provide early warnings, single alarms work independently.

Compare this to a proper CO detection system—the kind with multiple sensors throughout the building, connected monitoring, and the ability to alert everyone simultaneously. These systems can detect CO buildup earlier and in more locations, giving schools precious extra time to evacuate and address the source.

A school with only single-station alarms absolutely has a higher risk of delayed detection, especially in a negative air pressure situation where CO might be building up gradually in multiple areas.

What This Means for Your Child's School

I'm not trying to scare you, but I am trying to wake you up. The same conditions that caused the evacuation in Osceola exist in schools across the country. Tight building construction, aging HVAC systems, budget constraints, and inadequate CO detection create a perfect storm.

Here's what you can do:

1. Ask questions. Find out what type of CO detection your child's school has. Is it single alarms or a connected system? When were they last tested or replaced?

2. Know the signs. If your child comes home with headaches, nausea, or feeling unusually tired—especially if multiple kids are experiencing similar symptoms—don't ignore it.

3. Support proper funding. Quality CO detection systems cost money, but they're infinitely cheaper than the alternative. Advocate for proper safety equipment in your school's budget.

4. Share this information. Many school administrators don't fully understand the negative air pressure risk. Education is the first step toward prevention.

   
   

My boys were lucky. They survived their CO exposure and poisoning, and their experience led to stronger laws in the Commonwealth of Virginia. But I've met too many families who weren't as fortunate.

The incident in Osceola was a warning, not just for that community, but for all of us. Every school building in America could face similar conditions. The question is: will we act before the next evacuation, or will we wait until it's too late?

Our children deserve better than being unprotected guinea pigs in buildings that weren't designed with their safety as the top priority. It's time to take negative air pressure and carbon monoxide protection in schools seriously.