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

IS 11360: Scope - Key Specifications & Formulas

Scope Summary:

• Standardizes smoke detectors and measuring instruments for fire detection.
• Enables users to select standard devices and manufacturers to produce standard detector heads.
• Covers light source, smoke generation, and measurement methods.

Key Specifications

• Light Source:
  • Tungsten filament automotive lamp energized at ~50% rated voltage for uniform light intensity (Clause 3.1).
• Smoke Generation:
  • Use Whatman No. 2 filter papers (80-110 g/m²) on a hot plate to generate smoke by smouldering (Clause 1.5).
  • Optical density increase rate ≤ 0.2 dB/m/min, max ≥ 1.5 dB/m.
• Smoke Measuring Instrument:
  • Must be stable and proportional to smoke concentration (Appendix C).
  • For ionization/scattering detectors, use ionization/scattering chambers or meter in Appendix E.

Important Formula: Optical Density of Smoke (Appendix D)

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

• (L) = length of light path (m)
• (I_0) = light intensity without smoke
• (I_e) = light intensity with smoke

SI Units Used (Summary)

This concise scope helps ensure uniformity in smoke detection device manufacturing and testing.

IS 11360: Key Definitions and Specifications Summary

1. Definitions (Clause 2.0)

• Standard definitions apply to terms used in smoke detection and fire alarm systems.

2. Light Source (Clause 3.1)

• Tungsten filament automotive lamp used as light source.
• Operated at ~50% rated voltage for uniform light beam intensity.
• Photocell output ∝ smoke concentration.

3. International System of Units (SI Units)

4. Smoke Generation (Clause 1.5)

• Use circular hot plate with Whatman No. 2 filter papers (80-110 g/m²).
• Smoke generated by smouldering papers.
• Optical density increase rate ≤ 0.2 dB/m/min, max ≥ 1.5 dB/m.

5. Optical Density of Smoke (Appendix D)

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

• (I_0): Light intensity without smoke
• (I_e): Light intensity with smoke
• (L): Length of light path (m)

6. Smoke Measuring Instrument (Appendix C)

• Must be stable and linear.
• Output directly proportional to smoke concentration.
• Use ionization chamber

IS 11360: General Requirements (Clause 4.2) - Key Points

• Directional Dependence (4.1): Test one randomly selected detector from sample.
• Reproducibility & Optimal Sensitivity (4.2): Detectors must show consistent response under repeated tests.
• Supply Voltage Variation (4.6): Detectors must operate reliably within specified voltage ranges.
• Insulation Resistance (4.7): Minimum insulation resistance to ensure safety.
• Temperature Effects:
  • High Temperature (4.10) and Low Temperature (4.11) tests ensure detector performance under thermal extremes.
• Full Scale Fires (4.18): Detectors must respond correctly to simulated full-scale fire conditions.

Optical Density of Smoke (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
• Path length (l) in meters

Smoke Generation (Clause 1.5)

• Use Whatman No. 2 filter papers (80-110 g/m²)
• Smoke optical density increase rate ≤ 0.2 dB/m/min
• Max optical density ≥ 1.5 dB/m

Units (SI)

Summary Diagram

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

This ensures detectors meet sensitivity, stability, and environmental robustness per IS 11360.

IS 11360: Performance Tests & Criteria for Conformity

Key Tests & Clauses Overview (Clause 4.0 & Appendix A)

Example: Humidity Test (Clause 4.12)

Detector #7 is tested in a climatic chamber with above conditions, connected to control equipment.

Important Specification (Clause 3.8)

• Smoke entry openings: Minimum 30 mm below ceiling (assumed smooth and flat).

Summary Diagram of Test Flow

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

IS 11360: Marking and Identification - Key Points

1. Marking Requirements (Clause 5.1.1)

• Detectors may be marked with the ISI Certification Mark.
• ISI Mark ensures compliance with the standard under ISI's inspection, testing, and quality control.
• Use of ISI Mark is regulated by the Indian Standards Institution (Certification Marks) Act.

2. Detector Numbering and Tests (Appendix A, Clause 4.0)

• Detectors are identified by numbers corresponding to specific tests (e.g., reproducibility, stability).
• Tests include: Directional dependence, Reproducibility, Stability, Repeatability, Endurance, Voltage variation, Insulation resistance, Vibration, Shock, Temperature, Humidity, Corrosion, Ambient light, Transients, Dust, Full scale fires.
• Each detector number is marked as per the tests it has undergone.

3. Optical Density of Smoke (Appendix D)

• Optical Density (OD) formula:

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

  where:

  • (I_0) = Light intensity without smoke
  • (I_e) = Light intensity with smoke
  • (d) = length of light path in meters

4. Smoke Measuring Instrument (Appendix C & E)

• Instruments must be stable and proportional to smoke concentration.
• Different meters are used depending on detector type (ionization, scattering, light obscuration).

Summary Table: Key Marking & Identification Elements

flowchart LR
    A[Detector] --> B[Marking with Detector Number]
    B -->

IS 11360: Instructions & Technical Specifications Summary

Key Points from Clause 4.0 & Appendix A:

• Tests & Requirements cover detector performance aspects such as:

  • Directional dependence (Clause 4.1)
  • Reproducibility & optimal sensitivity (4.2)
  • Stability (4.3)
  • Repeatability (4.4)
  • Endurance (4.5)
  • Supply voltage variation (4.6)
  • Insulation resistance (4.7)
  • Environmental tests: vibration (4.8), shock (4.9), temperature extremes (4.10, 4.11), humidity (4.12), corrosion (4.14), dust (4.17), etc.

• Detector Marking & Sampling: Specific detectors (e.g., M2, M14) are selected for tests to ensure consistency.

Technical Specifications Highlights:

• Light Source (Clause 3.1):

  • Tungsten filament automotive lamp used.
  • Operated at ~50% rated voltage for uniform intensity.
  • Photocell output proportional to smoke concentration.

• Reset Time Variation (r.t.v.):

  • Ratio of highest to lowest r.t.v. ≤ 1.6.
  • Average r.t.v. calculated from tests (M2, M14).

SI Units & Definitions (for reference):

Summary Table: Selected Tests & Clauses

IS 11360: Test Schedule Key Points & Specifications

Sample Size & Scope:

• 15 detectors randomly selected from ≥ 200 units.
• Tests cover production of 10,000 detectors.
• Detectors numbered 1 to 15 for identification.

Test Schedule Summary (Appendix A):

Humidity Test Details (Clause 4.12):

• Detector #7 tested inside climatic chamber with above conditions.
• Connected to control and indicating

Measurement of Relative Transmittance Value (r.t.v.)
As per IS 11360 Appendix B (Clauses 4.1 to 4.17)

Key Specifications & Procedure:

• Wind Tunnel Conditions (IS 9972-1981 Fig.6):
  • Air velocity: 0.2 ± 0.05 m/s
  • Air temperature: 25 ± 5°C
• Detector Mounting:
  • On top horizontal section of tunnel
  • In least favourable orientation (determined by directional dependence test)
• Smoke Generation:
  • As specified in Appendix B-2
• Measurement:
  • Detector powered and warmed up as required
  • Smoke density measured at the instant detector alarms using an optical density meter (Appendix C) placed close to detector
  • Recorded smoke density = r.t.v.

Important Limits and Calculations:

• Average r.t.v. for detectors is calculated from test results (designated M2 and M14).

Summary Formula for r.t.v.

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

flowchart LR
    A[Wind Tunnel Setup] --> B[Detector Mounted (Least Favourable Orientation)]
    B --> C[Smoke Generation]
    C --> D[Detector Alarm Initiation]
    D --> E[Measure Smoke Density with Optical Density Meter]
    E --> F[Record r.t.v.]

Note: Detector must be reset immediately after each r.t.v. measurement to ensure reproducibility.

IS 11360: Optical Density Meter Key Details

Optical Density (OD) Formula (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
• Path length (l) in meters (m)

Optical Density Meter Components (Appendix E & Clause 1.1)

Smoke Generation & Measurement (Clause 1.5)

• Filter paper bundle diameter ≤ heater plate diameter
• Smoke generation rate controlled to increase OD ≤ 0.2 dB/m/min
• Maximum OD ≥ 1.5 dB/m
• Use same filter paper type throughout tests

Functional Flow (Schematic Overview)

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

Notes

• The meter output is directly proportional to smoke concentration.
• Stability and linearity of the sensor and instrument are critical.
• Measurements follow the "light obscuration" principle.

This setup ensures reliable, repeatable smoke optical density measurement per IS 11360 standards.