Guide to Achieving A Positive Integrity Test

Historically the vast amounts of discharge test failures have been caused by lack of enclosure integrity. The proper initial concentration is achieved, but the enclosure doesn’t retain it for the required time. The Enclosure Integrity Test is a suitable alternative means of verifying adequate enclosure integrity for total flooding systems. Greater overall fire protection of the hazard will be obtained through having at least a one-hour fire rated separation surrounding the enclosure. Compartmentation is considered one of the key first elements in effective fire protection. Greater environmental control (humidity, dust and temperature) and lower ongoing maintenance costs will be provided by a tight enclosure. Greater protection from smoke contamination originating outside the hazard is obtained with a tight enclosure. The increased cost of providing additional drywall and dampers will be offset by lower maintenance costs, possibly lower initial acceptable test costs if a discharge test is not performed and also reduced costs to maintain an acceptably tight enclosure over time. Authorities now require periodic Enclosure Integrity Testing to ensure continued performance. Slab to slab walls make the enclosure easier to ‘re-accept’ in the future

1.0 Penetration Planning

Achieving and maintaining a high degree of room tightness is facilitated by having the location and design of certain penetrations, specifically for cables, planned in advance. The installation of round pipe sleeves or other engineered re-sealable openings is recommended. Sufficient extra capacity should be installed to handle expected future expansion. Sealing openings between cables within bundles is a very common and difficult problem to solve once all cables are in place.

1.2 HVAC Dampers

All ducts leading into or out of the space must be mechanically dampered, even if the air handler serving them will be shutdown and the ducts terminate at ceiling level. Dampers should be smoke rated (See Section 4.00).

1.3 Minimum Protected Height

Even if a protected enclosure is designed and built to be as tight as possible, a certain degree of leakage must be expected to occur.

The Leakage Mechanism is as follows:

During the retention period, the agent/air mixture, being heavier than air, will generally leak out of lower openings. Air will enter through openings high in the room at the same rate to replace it. If air-moving devices in the room are shutdown, this incoming air tends to collect at the top of the room. The upper level of the suppressant mixture descends over time. This boundary layer between the original suppressant/air mixture and the infiltrated air is known as the descending interface.

However, if any air moving equipment is left on during the retention period (blowers, air conditioning units, and UPS equipment), the incoming air becomes completely mixed with the original agent/ air mixture. This causes the average concentration throughout the room to decay. This phenomenon is known as mechanical mixing.

If a descending interface forms, the allowable height to which it can descend in 10 minutes is a crucial factor. This minimum protected height is usually where the upper probe would have been placed during a discharge acceptance test (tallest equipment cabinets, usually consisting of essential equipment).

The minimum protected height is best defined as: the highest combustible item in the room in certain cases the most essential item of equipment is utilized as the required protected height. Design the room and its equipment (cable trays are the most common problem) so that all combustibles are kept below the 75% level (measured from the floor slab).

Small rooms (say up to approx. 200 cubic metres) have historically been the most difficult to pass using a discharge test. There appears to be one of two reasons for this. One is that the suppressant is more likely to be lost during the initial discharge, especially if there is an unprotected ceiling void above.

The predominant reason appears to be because small rooms have much less favourable surface to volume ratios. For example, a 400 cubic metre room has ten times the volume of a 40 cubic metre room, but has only three times the wall area. Relatively speaking, the small room has to be much tighter to retain the agent. As the Room Integrity Test is even more stringent that the discharge test. This can make small rooms difficult to accept if they aren’t practically airtight.

2.0 Enclosure Integrity Specifications

On new installations, it is generally the Main Contractor, who is responsible for the overall room tightness and in turn would require that all sub-contractors perform the necessary sealing, which relates to their work. Any work being done on the construction by second level contractors (e.g. cable installers) not operating under the Main Contractor must also be subjected to this requirement under their contracts. If the suppressant system is being installed as a retrofit, one contractor must be made responsible for sealing existing holes.

In order to pass the Enclosure Integrity Test, the contractor may have to seal items, which are not specifically described, in the prescriptive specifications. Item 2.3 covers just about every possibility.

2.1 Enclosure Integrity Performance Specification

Enclosure leakage shall be eliminated to at least the degree necessary to enable the suppressant protected enclosure to pass a test conducted in accordance with the Enclosure Integrity Procedure.

2.2 Enclosure Integrity Prescriptive Specifications

The following items cover enclosure leakage in a general fashion, and should be placed in the General Contractors Specification. If the client or authority requires that the materials and techniques used must produce a one or two-hour fire rated enclosure, this must be specified.

Because historically the walls and roof of unprotected ceiling voids above suspended ceilings have not had to be well sealed to retain and agent, existing building practice, if retained, will produce enclosures where large leakage areas will be measured, resulting in unacceptably low predicted retention times. It is recommended that where possible the walls and roofs of unprotected ceiling voids be sealed as tightly as the protected enclosure below.

2.3 General / Standard Sealing Requirements

The perimeter walls of the protected enclosure shall extend from the structural floor to the structural floor above, or the roof / solid slab ceiling level. Alternatively: The (suspended) ceiling of the enclosure shall be of a solid plasterboard construction, taped and painted. Access panels may be required if access is essential.

Where an under floor space continues out of the suppressant protected area into adjoining rooms, airtight fire rated partitions shall be installed under the floor directly under above-floor border partitions. These partitions shall be caulked top and bottom. If a removable floor tile extends under a doorway over such a partition, it shall either be: permanently sealed in place; installed with a flexible seal between it and the wall below; or the tile shall be discontinued at the doorway with a permanent airtight ledge created up to which the floor tiles abut.

If adjoining rooms share the same under floor air handlers, then the partitions shall have dampers installed of the same type as required for ductwork.

All holes, cracks, or penetrations leading into or out of the protected area shall be sealed. Pipe chases and cable trays shall be sealed around both the outside and inside at a point where they pass through the envelope of the protected zone. All walls shall be caulked around the inside perimeter of the room where the walls rest on the floor slab and where the walls intersect the ceiling slab or roof above.

Porous block walls shall be sealed slab-to-slab to prevent gas from passing through the block. Multiple coats of paint may be required.

All doors shall have door sweeps or drop seals on the bottoms, weather stripping around the jambs, latching mechanisms and door closure hardware. In addition, double doors shall have a weather stripped astral to prevent leakage between doors and a coordinator to assure proper sequence of closure.

Windows shall have a solid weather stripping around all joints. Glass to frame and frame to wall joins shall be sealed.

All unused and out-of-service ductwork leading into or from a protected area shall be permanently sealed off (airtight) with metal plates caulked and screwed in place at the point where they breach the envelope of the protected zones.

The possibility of ceiling tiles being displaced during a discharge should be addressed at the design stage. Possible options include tile clipping, nozzle deflectors, lowering the nozzles a certain distance from the ceiling and ensuring proper nozzle location. Contact suppressant equipment manufacturers for guidance.

3.0 Suppressant System Specifications

This section covers only the issue relating to the suppressant system design, which has an impact on the Enclosure Integrity Test.

The system shall be designed and installed to provide an adequate concentration throughout the protected enclosure upon discharge, as calculated. The protected enclosure extends from the floor slab to (the slab above) (the suspended ceiling). The following rooms are considered to constitute the suppressant protected zone.

4.0 HVAC Specifications

Ductwork in service with the building air handling unit shall have gasketed low leak agent/smoke type dampers with flexible seals. Rigid metal-to-metal blade seals should not be used. Dampers shall be spring-loaded or motor-operated to provide near airtight shut-off. (Option: The dampers should be of the spring close, motor open type – to provide a fail-safe facility.)

The dampers should be installed as close as possible to the duct's point of entry into the room. All duct joints between the damper and the duct entry point should be sealed, as should the gap between the damper frame and the wall. An access panel should be installed to permit inspection of the damper.

It is recommended that whenever possible, any in-room air conditioning units be shut down upon discharge to reduce the possibility that they will expel the mixture from the sub-floor.

Ideally, the suppressant protected enclosure will be a "dead" room from the static pressure standpoint by the time the suppressant discharges. If the dampers are truly tight, and the in-room air conditioning units are shut down, close to zero pressure is usually achieved. Occasionally, however, significant imbalances exist in the building HVAC system, which could increase the leakage of suppressant from the enclosure.

If a significant static pressure is uncovered during the Enclosure Integrity Test which is not solved by improving damper seals or sealing leaks, it may prove to be necessary to have that zone of the building’s air handlers shut down in addition to closing the dampers.

5.0 Approval/ Acceptance of Suppressant System

Historically, the vast majority of discharge test failures have been caused by lack of enclosure integrity.

Nonetheless, if a discharge test is not being carried out, it is essential that other aspects of the system installation be verified and tested.

The contractor shall provide a test report. After the tests are completed and the system has been accepted, the system shall be brought to full operating condition.

It is important to note that while the suppressant contractor is often responsible for providing the Enclosure Integrity Test, he is not responsible for the sealing unless specifically stated in his contract.