Warehouse Fire Tests – Smoke Detectors

October 29th, 2010 Print This Post Print This Post

Xtralis, a maker of Aspirating Smoke Detection (ASD) solutions, conducted a series of fire tests in a warehouse setting to demonstrate the capabilities of three smoke detection technologies, an air-sampling solution, a spot-type detector and a beam detector.

Warehouse Fire Test

Xtralis, a maker of Aspirating Smoke Detection (ASD) solutions, conducted a series of fire tests at Victoria University’s Werribee Campus in 2008. The purpose of these tests was to demonstrate the smoke detection capabilities of three detection technologies during early developing stages of fires in a warehouse environment.

Three small-scale fire/smoke tests were conducted using three fuels, smoke pellets, N-Heptane and timber logs. In this series of fire tests the ASD solution outperformed the spot and beam detectors.

The performances of three smoke detector technologies are compared for use in a warehouse environment. Video by Xtralis

Fire Detection Solutions

Several types of smoke detection technologies are available – spot detectors, beam detectors, rate of heat rise detectors, and ASD solutions.

  • Spot Detectors, also called point detectors, are one of the most common types of smoke detectors used today. Spot detectors are “passive” in that they wait for smoke to enter a detection chamber, where an optical sensor and/or an ionization sensor identifies the presence of smoke.
  • Beam Detectors bounce a beam of light between two sensors to detect the presence of smoke. When a significant level of smoke disrupts the beam, an alarm is activated. Beam Smoke Detectors are used to provide smoke detection for large areas and they are used in situations where it is impractical or inappropriate to use spot detectors. Example applications are aircraft hangers, historic buildings, museums, manufacturing plants, petrochemical plants and warehouses.
  • Rate of Heat Rise Detectors measure the rapid rise of ambient room temperature to identify the threat of a fire. They work by sensing the temperature rise of a heat sensitive element located within the device. Rate of rise detectors may not respond to small developing fires with low energy release rates. To address this downside combination detectors are applied, which add a fixed temperature element that will responds when the fixed temperature element reaches the threshold (trigger) temperature. Rate of Heat Rise detectors are often integrated with fire suppression systems and are typically mounted on ceilings where heat from a fire collects.
  • Aspirating Smoke Detection solutions are designed to detect the earliest presence of a fire. The sampling chamber of the ASD is based on a nephelometer that is capable of detecting the presence of smoke particles suspended in air. The air samples are transported through a dual-stage filter to remove dust and other contaminants that can cause false alarms. Air samples pass through a highly sensitive centralized laser detection unit. Besides their use in warehouse and distribution centers, they are also used in high-value or high-challenge environments such as, computer rooms, laboratories, clean rooms, data centers, museums, atriums, elevator shafts and aircraft hangars.

Applications

A spot detector will detect fires close to the ceiling earlier than beam type smoke detectors. This is because a localized concentration of smoke will reach a spot type detector before a sufficient “cloud” will develop to trigger beam type detectors. However, in cases where there is considerable air dilution of smoke, a beam type detector is advantaged, because the less dense (concentrated) smoke layer will result in a smaller localized concentration of smoke reaching a spot-type detector, and which in turn will take longer to reach its alarm threshold.

The structural make up of ceilings, smooth vs. nonsmooth ceilings, also plays an important role in the choice of these type of smoke detectors. While both types of detectors can be mounted close to the ceiling, if structural beams project downward from the ceilings i.e., nonsmooth ceilings, NFPA 72 will require spot type detectors to be placed in the pockets formed by these beams. Many warehouses have these type of nonsmooth ceilings. In these cases beam type detectors may be difficult to install due to their minimum spacing requirement between transmitter and receiver (30ft – 50ft).

Aspirating smoke detectors are not recommended for use in unstable environments. The reason for this is the wide range of particle sizes that are detected. However, this does not mean that they cannot be used in dusty or dirty environments – as long as the levels of aerosol remain stable. For example, one of many applications for ASD are cold storage facilities with high air flow. Here the environmental conditions are outside the tolerance of typical fire detection technologies and sampling points are often located inside the cold storage space.

Smoke detectors are not required in warehouses that are sprinklered (in US) – with the exception of cold storage or specialty warehouses. Nevertheless, building owners may opt to use smoke detectors to improve the overall fire safety design of their facilities, especially in high value environments.

Fire Codes

Any of these type of smoke detectors – once they are installed must comply with state and local fire and building code regulations. Specifically, compliance with NFPA 72 is often required. In any case, the Authority Having Jurisdiction (AHJ) will review compliance with all necessary fire protection and regulation requirements.

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