Pressurized Building HVAC Technical Requirements

This article is about Pressurized Building HVAC Technical Requirements as per International Codes and standards.

Pressurized Building HVAC Technical Requirements

1. “Buildings located in Class I, Zone 2 or Class I, Division 2 electrical areas shall be maintained at the positive pressure of 0.1 inch water gauge. (NFPA 496 Para 7.4.1)
   Note: See Item No. A2 in this SAIC for Control Building “
2. Control building shall be maintained at a positive pressure of o.25 inch water gauge with all the opening closed.
3. Pressurization fans, or air-handling units providing building pressurization, shall be provided with 100% standby units, powered from a separate or emergency power supply.
4. Air intake of a pressurized building shall be located in a nonclassified area, be at least 4.5 m above any classified electrical area, and at least 7.5 m above grade. (SAES-B-014 Para 9.4)
5. For all pressurized buildings a differential pressure sensor shall be installed for measuring the static pressure difference between the interior and exterior of the building. The external static pressure probe shall be shielded from the dynamic effect of the wind.
6. In pressurized buildings all status indicator lights, manual switches and alarms that are part of the pressurization system shall be located on the process control panel of the building, visible and readily accessible to the operators.
7. At loss of airflow through the operating fan providing pressurization, the standby fan shall start automatically.
8. An alarm shall alert personnel to such a condition.
9. Both the primary and standby fans shall each have a backdraft damper for the prevention of air short-circuiting.
10. The outside air intake duct shall have motorized shut-off damper interlocked with the pressurization fans and a manually operated volume damper
11. In hazardous (Class I, Zone 2 or Class I, Division 2) areas or areas defined by the building risk assessment, appropriate gas detectors shall be installed in the outside air intake stream to detect toxic or flammable gases.
12. At the predetermined gas concentrations* an alarm shall be activated, and all outside air intake into the building shall be shut off automatically.

Alarm shall be activated at the gas concentration in level determined by designers/proponete and any other involved responsible parties in accordance with SAES-B-014.

Standards Codes and References For Pressurized Building HVAC

1. SAES-K-001 – Heating, Ventilating and Air Conditioning (HVAC).
2. SAES-K-100 – Saudi Aramco Mechanical (HVAC) Code.
3. Uniform Mechanical Code (UMC).
4. Uniform Fire Code (UFC), 1997.
5. NFPA 496 – Standard for Purged and Pressurized Enclosures for Electrical Equipment, 2008.
6. SAES-B-014 – Safety Requirements for Plant and Operations Support Buildings.
7. SAES-K-002 – Air Conditioning Systems for Essential Operating Facilities.
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