Specification for smoke detectors for use in an automatic electrical fire alarm system
1985 Edition

Overview of Scope in IS 11360

• Establishes standards for smoke detectors and their measurement tools in fire detection.
• Facilitates selection of standardized devices by users and ensures manufacturers produce uniform detector units.
• Includes specifications for light sources, smoke production, and measurement techniques.

Essential Specifications

• Light Source: Tungsten filament automotive lamp operated at approximately 50% of rated voltage to maintain consistent light intensity.
• Smoke Generation: Smoke produced by smouldering Whatman No. 2 filter papers, weighing between 80 and 110 g/m², placed on a heated plate.
• Smoke optical density increment rate limited to 0.2 dB/m/min with a maximum of 1.5 dB/m.
• Smoke Measurement Instruments: Instruments must be stable, with output proportional to smoke concentration, utilizing ionization or scattering chambers as specified.

Important Formula for Optical Smoke Density

[ \text{Optical Density (dB/m)} = \frac{10}{L} \log_{10} \frac{I_0}{I_e} ]

where (L) is the light path length in meters, (I_0) the light intensity without smoke, and (I_e) the intensity with smoke.

Summary of SI Units Used

This scope ensures uniformity in manufacturing and testing procedures for smoke detection devices.

Essential Definitions and Specifications in IS 11360

Definitions (Clause 2)

• Standardized terminology for components and concepts related to smoke detectors and fire alarm systems.

Light Source Details (Clause 3.1)

• Utilizes tungsten filament automotive lamps.
• Operated at roughly half the rated voltage to ensure a uniform light beam.
• Photocell output corresponds proportionally to smoke concentration.

SI Units Reference

Smoke Generation Method (Clause 1.5)

• Employed circular hot plate with Whatman No. 2 filter papers of 80-110 g/m².
• Smoke generated by smouldering the filter papers.
• Optical density increase rate restricted to 0.2 dB/m/min, with a maximum of 1.5 dB/m.

Optical Density Calculation (Appendix D)

[ \text{OD (dB/m)} = \frac{10}{L} \log_{10} \left(\frac{I_0}{I_e}\right) ]

where (I_0) is the light intensity without smoke, (I_e) with smoke, and (L) the path length.

Smoke Measurement Instruments (Appendix C)

• Instruments must maintain stability and output proportionality.
• Ionization or scattering meters are used depending on detector type.

Highlights of General Requirements (Clause 4.2) in IS 11360

• Directional Dependence (4.1): Randomly select one detector from the batch for testing direction sensitivity.
• Reproducibility and Sensitivity Consistency (4.2): Detectors must demonstrate repeatable and optimum sensitivity in tests.
• Voltage Variation Handling (4.6): Devices should perform reliably within specified voltage fluctuations.
• Insulation Resistance (4.7): Minimum insulation resistance levels to guarantee electrical safety.
• Temperature Resistance: Tests at elevated (4.10) and reduced (4.11) temperatures to confirm detector function under thermal stress.
• Full-Scale Fire Response (4.18): Detectors must respond appropriately to simulated full-scale fire scenarios.

Optical Density Formula (Appendix D)

[ \text{OD (dB/m)} = 10 \times \log_{10} \frac{I_0}{I_e} ]

• (I_0): Intensity of light in absence of smoke
• (I_e): Intensity of light in presence of smoke
• Path length (l) in meters

Smoke Generation Details (Clause 1.5)

• Employ Whatman No. 2 filter papers (80-110 g/m²)
• Optical density increase rate limited to 0.2 dB/m/min
• Maximum optical density maintained at or above 1.5 dB/m

SI Units Summary

Flowchart Summary

flowchart LR
    A[Smoke Generation] --> B[Optical Density Meter]
    B --> C[Detector Performance Testing]
    C --> D{Test Types}
    D -->|Directional Dependence| E[Clause 4.1]
    D -->|Reproducibility| F[Clause 4.2]
    D -->|Voltage Variation| G[Clause 4.6]
    D -->|Temperature Tests| H[Clauses 4.10,4.11]
    D -->|Full Scale Fires| I[Clause 4.18]

This framework ensures detectors meet performance, stability, and environmental durability requirements.

Performance Evaluation and Compliance Tests in IS 11360

Overview of Tests (Clause 4.0 & Appendix A)

Example: Humidity Exposure Test (Clause 4.12)

Detector number 7 is subjected to this controlled climatic chamber environment, connected to control and monitoring apparatus.

Additional Specification (Clause 3.8)

• Smoke entry apertures must be positioned at least 30 mm below a smooth and flat ceiling surface.

Testing Process Flow

flowchart TD
    A[Start: Detector Sample] --> B[General Requirement Tests]
    B --> C{Directional Dependence Required?}
    C -->|Yes| D[Directional Test]
    D --> E[Reproducibility & Sensitivity Assessment]
    C -->|No| E
    E --> F[Environmental Conditioning Tests]
    F --> G[Electrical Integrity Tests]
    G --> H[Full Scale Fire Simulation]

This sequence ensures thorough verification of detector sensitivity, durability, and operational robustness.

Marking and Identification Requirements in IS 11360

Marking Guidelines (Clause 5.1.1)

• Devices may bear the ISI Certification Mark, signifying compliance with Indian standards.
• The ISI mark placement is governed by the Indian Standards Institution (Certification Marks) Act and ensures ongoing inspection and quality control.

Detector Numbering and Test Identification (Appendix A, Clause 4.0)

• Each smoke detector is assigned a unique identifier corresponding to specific performance tests it has undergone.
• Tests include directional dependence, reproducibility, stability, repeatability, endurance, voltage variation, insulation resistance, vibration, shock, temperature, humidity, corrosion, ambient light, transient conditions, dust exposure, and full-scale fire simulation.

Optical Density Formula (Appendix D)

[ \text{OD (dB/m)} = 10 \log_{10} \frac{I_0}{I_e} ] where (I_0) is the intensity without smoke, (I_e) with smoke, and (d) the path length in meters.

Smoke Measurement Instrument Requirements (Appendices C & E)

• Instruments must be stable and provide linear output proportional to smoke concentration.
• Different types of meters are employed depending on detector technology (ionization, scattering, or light obscuration).

Summary Table: Marking and Identification Elements

flowchart LR
    A[Detector Unit] --> B[Marking with Test Numbers and ISI Mark]

This ensures traceability and quality assurance throughout the detector lifecycle.

Summary of Instructions and Technical Specifications in IS 11360

Key Testing and Performance Requirements (Clause 4.0 & Appendix A)

• Tests cover aspects such as:
  • Directional dependence (4.1)
  • Reproducibility and optimal sensitivity (4.2)
  • Stability (4.3)
  • Repeatability (4.4)
  • Endurance (4.5)
  • Variations in supply voltage (4.6)
  • Electrical insulation resistance (4.7)
  • Environmental exposures including vibration (4.8), shock (4.9), high and low temperature (4.10, 4.11), humidity (4.12), corrosion (4.14), and dust (4.17).

Detector Marking and Sampling

• Specific detectors such as M2 and M14 are chosen for repeatability and sensitivity tests to ensure consistent quality.

Technical Specifications Highlights

• Light Source (Clause 3.1): Tungsten filament automotive lamp operated at roughly 50% rated voltage for consistent light output.
• Reset Time Variation (r.t.v.): Ratio of maximum to minimum r.t.v. should not exceed 1.6; average r.t.v. calculated from key detectors.

Reference SI Units

Summary Table of Key Tests

This section lays out comprehensive instructions to ensure detector quality and operational reliability.

Overview of Test Schedule as per IS 11360

Sample Size and Scope:

• A batch of 15 detectors randomly chosen from a production lot of at least 200 units.
• The tests are designed for batches producing up to 10,000 detectors.
• Each detector is assigned a number from 1 to 15 for identification.

Summary of Test Schedule (Appendix A)

Humidity Test Parameters (Clause 4.12)

Detector number 7 undergoes testing inside a climatic chamber under these conditions and is connected to control and indicating systems.

Procedure for Measuring Relative Transmittance Value (r.t.v.) According to IS 11360 Appendix B

Test Environment and Setup

• Wind Tunnel Conditions (as per IS 9972-1981 Fig.6):
  • Airflow velocity maintained at 0.2 ± 0.05 m/s
  • Ambient air temperature maintained at 25 ± 5 °C
• Detector Installation:
  • Positioned on the top horizontal section of the tunnel
  • Installed in the orientation found least favorable by directional dependence testing
• Smoke Generation:
  • Conducted as per Appendix B-2 specifications
• Measurement Protocol:
  • Detector powered and warmed up before testing
  • Smoke density measured at the moment the detector triggers an alarm using an optical density meter placed close by
  • Recorded smoke density at alarm is the r.t.v.

Acceptance Criteria and Limits

• Average r.t.v. values computed from detectors M2 and M14 test results.

Formula for r.t.v.

[ \text{r.t.v.} = \text{Smoke Density at Alarm Trigger (dB/m)} ]

Test Flow Diagram

flowchart LR
    A[Wind Tunnel Setup] --> B[Mount Detector in Least Favorable Position]
    B --> C[Generate Smoke]
    C --> D[Detector Alarm Activation]
    D --> E[Measure Smoke Density Using Optical Meter]
    E --> F[Record r.t.v.]

Note: Detectors must be reset immediately after each measurement to maintain consistency.

Details of Optical Density Meter as per IS 11360

Optical Density Calculation (Appendix D)

[ \text{OD (dB/m)} = 10 \times \log_{10} \frac{I_0}{I_e} ]

• (I_0): Light intensity without smoke
• (I_e): Light intensity with smoke
• (l): Length of light path in meters

Components of Optical Density Meter (Appendix E & Clause 1.1)

Smoke Generation and Measurement (Clause 1.5)

• Bundle diameter must not exceed heater plate diameter
• Smoke generation rate controlled to increase optical density at no more than 0.2 dB/m per minute
• Maximum optical density maintained at or above 1.5 dB/m
• Consistent use of same filter paper type across tests

Functional Flow Schematic

flowchart LR
    A[Light Source: Tungsten Lamp] --> B[Condensing Lens (L1)]
    B --> C[Smoke Chamber with Filter Papers]
    C --> D[Collimating Lenses (L2 & L3)]
    D --> E[Photocell Sensor (Selenium Cell)]
    E --> F[Output: Optical Density Reading]

Additional Notes

• The meter output is directly proportional to smoke concentration.
• Sensor stability and linearity are critical for accurate measurement.
• The measurement principle is based on light obscuration.

This design provides dependable and reproducible optical density measurements in accordance with IS 11360.