What does positive pressure in ventilation mean?
This is a situation where more air is supplied into a room than is exhausted from it. As a result, the interior has higher pressure than the surrounding area, and air escapes through gaps, vents, or openings to the outside.
What are the benefits of positive pressure?
- Protection: It protects the interior from dust, exhaust fumes, and moisture.
- Air Quality: It improves air quality and workplace comfort.
- Odour Control: It limits the influx of unpleasant smells from outside.
Where is positive pressure ventilation used?
In locations where the air must remain clean and stable:
- Server rooms, laboratories, and offices.
- Clean warehouses.
- Precision production zones or technical rooms with sensitive electronics.
What are the disadvantages?
In areas where pollutants are generated (e.g., dust, moisture, fumes), positive pressure can spread them throughout the entire facility. It can also cause dirt to accumulate within the room itself if the exhaust system is not operating effectively.
What is negative pressure?
Negative pressure occurs when the exhaust system removes more air than is supplied. This creates lower pressure inside the room, causing fresh air to flow in from the outside or from adjacent zones.
Where is negative pressure ventilation used?
In areas where dirty, humid, or toxic air must be extracted:
- Swimming pools, industrial kitchens, and chemical laboratories.
- Production halls with high levels of dust or fumes.
Advantages of negative pressure in ventilation
- Containment: It keeps pollutants within the source room.
- Protection: It protects adjacent zones from moisture, chlorine, dust, or fumes.
- Safety: It improves occupational safety and hygiene.
Disadvantages of negative pressure
It can cause drafts and the influx of unfiltered air. It also increases heating and cooling costs because the "sucked-in" air must be treated. Excessive negative pressure makes opening doors difficult and can disrupt other systems (e.g., chimney backdrafting).
How to maintain balance in ventilation?
The best practice is to maintain a slight excess of supply or exhaust (usually 5–10%), depending on the room type:
- Clean zones → slight positive pressure.
- Dirty zones → slight negative pressure.
What are the most common mistakes?
- Lack of balance between supply and exhaust airflow.
- Excessive pressure differences between rooms.
- Poor fan regulation or the absence of a compensation system.
