To understand building pressures you have to understand building science.
A building's pressure should be as close to zero as possible. This is rarely the case. Many factors contribute to pressures. Building tightness, the less holes there is in a building the better off the building is. The tighter a building, the better.
Duct systems. The tighter the duct system the better. In a high negative pressure building the greater for concern of health & safety and high energy usage. The higher positive pressure the less concern for health & safety but still higher energy bills.
Our blog regarding building evaluation. The building owners negative pressures was at -7.2. Not only was he wasting energy also the CO was being back drafted from his gas fired appliance. Any negative pressure exceeding -3 Pa "pascals" is at risk of back drafting gas fired equipment. Not only back drafting occurs it also may cause flame roll out.
Flame roll out is a term used for gas fired equipment that has burner compartments that is open to the atmosphere. Furnaces, hot water heaters, boilers.
At -7.2 pa the human body cannot feel this pressure. We use manometers to discover and measure pressures.
Within several minutes of taking measurements will provides us with enough information to start our investigation on where and what to look for.
If you review our page on building pressures this will help you understand about pressures. Pa, hpa.