How can Sigma Power Tech Fix Low Air Pressure in Shelter Control System?

There are very few things more unsettling than seeing a warning light or alarm go off on your shelter control panel — especially when it is related to air pressure. For anyone responsible for managing a protected facility, a low air pressure warning is not something you ignore or push to the back of your to-do list. It needs attention, and it needs it quickly.

But before you panic or immediately call for an emergency service visit, it helps to understand what this warning actually means, what commonly causes it, and what steps you can walk through to identify and resolve the issue. That is exactly what this blog covers — in plain language, without making things more complicated than they need to be.

What Does a Low Air Pressure Warning Actually Mean?

To understand why this warning matters, you first need to understand the role air pressure plays inside a protected shelter.

A properly functioning Shelter Control System maintains slightly higher air pressure inside the facility compared to the outside environment. This is intentional. When internal pressure is higher, air flows outward through any gaps or openings rather than inward. That outward flow is what keeps contaminated or harmful air from the outside from finding its way in.

When the system detects that this internal pressure has dropped below the required level, it triggers a warning to alert the facility manager or operator. It is the system doing exactly what it is designed to do — flagging a condition that could compromise the shelter's ability to protect the people inside.

So a low air pressure warning is essentially the shelter telling you — something has changed, and we need to look at it.

Do Not Ignore It and Do Not Panic

The first and most important thing to do when you see this warning is to stay calm and treat it as a priority without overreacting. A low pressure warning does not automatically mean the shelter has been compromised or that there is an immediate danger. It means something in the system needs to be checked and corrected.

Walking away from it or resetting the alarm without investigating the cause is where things can go wrong. The warning will likely come back, and if the underlying issue is left unaddressed for too long, it can develop into a more serious problem — especially during an actual emergency when the shelter needs to perform at its best.

Check the Most Common Causes First

When a shelter system throws a low air pressure warning, there are a handful of usual suspects that are worth checking before anything else.

Doors and entry points not fully sealed. This is the most frequent cause of pressure loss. If a blast door, airtight door, or access hatch is even slightly ajar, or if a seal around a door has worn down over time, air will escape and pressure will drop. Walk through the facility and physically check every entry point. Make sure every door is fully closed and that the seals around them are intact with no visible gaps, cracks, or wear.

Ventilation valves left in the wrong position. Sometimes during routine maintenance or testing, a valve gets left open or in a position it should not be in during normal operation. Check the status of all blast valves and airtight valves to make sure they are set correctly for the current operating mode.

Filters that need replacing. When air filters become clogged or heavily loaded over time, airflow through the system is restricted. This restriction can cause the pressure balance inside the shelter to shift. Check when filters were last serviced and whether they are due for a replacement.

Fan or blower performance issues. The fans responsible for pushing filtered air into the shelter are critical to maintaining pressure. If a fan is running slower than it should, or not running at all due to a mechanical fault or power issue, pressure will drop. Check that all fans are operating normally and listen for any unusual sounds that might indicate a mechanical problem.

After You Have Checked the Basics

If you have gone through all of the above and the warning persists, the next step is a more thorough inspection of the system — ideally with the support of the team that installed and maintains it.

At this stage, the issue may be something less visible, such as a small leak in a duct, a sensor that needs recalibration, or a control setting that has drifted from where it should be. These kinds of issues are not always easy to spot without proper diagnostic tools and familiarity with the specific system installed in your facility.

This is where having the right service relationship in place makes a significant difference. At Sigma Power Tech, we are both the manufacturer of shelter control systems and the service provider for the facilities we work with. That means when something like a persistent low pressure warning comes up, our team already knows the system — how it was designed, how it was installed, and how it should be performing. We do not need to start from scratch to diagnose the issue.

Prevention Is Always Better Than Fixing

The honest truth is that most low air pressure warnings can be prevented with regular, well-documented maintenance. Seals degrade over time. Filters load up. Fans accumulate wear. These are natural processes, but they are also predictable ones — which means they can be managed before they cause a warning to appear.

Facilities that have a structured maintenance schedule in place, with periodic pressure testing and seal inspections built into the routine, almost always catch these issues early. Facilities that only check things when a warning appears are the ones that end up in more difficult situations.

If your facility does not currently have a maintenance plan in place for your shelter system, that is the most valuable thing you can put in place right now — not just to avoid warnings, but to ensure the system is genuinely ready the moment it is actually needed.

The Takeaway

A low air pressure warning from your shelter control system is a signal, not a catastrophe. It means your system is monitoring correctly and flagging a condition that needs your attention. Respond to it calmly, work through the likely causes in an organised way, and make sure the underlying issue is fully resolved rather than simply silenced.