Code of practice for fire safety of buildings (general): General principles of fire grading and classification

IS 1641: Scope Summary

• Scope: IS 1641 covers methods for determining fire resistance of building materials and elements.
• Rounding off values: Per IS 2:1960, test or calculation results must be rounded to the same number of significant figures as specified in IS 1641.
• Calorific values & hazardous materials: Removed from this standard; refer to standard textbooks or the upcoming Handbook on Fire Protection.
• Application: Ensures uniformity in fire resistance testing and reporting.

Key Specification from IS 2:1960 (Rounding off)

Summary Diagram of Scope Application

flowchart TD
    A[Start: Fire Resistance Test] --> B{Calculate/Observe Value}
    B --> C[Round off per IS 2:1960]
    C --> D[Compare with IS 1641 Specified Values]
    D --> E{Complies?}
    E -->|Yes| F[Accept Result]
    E -->|No| G[Review Test/Analysis]

For detailed fire resistance methods, refer to the full IS 1641 document and related fire protection handbooks.

Fire Load and Hazard Assessment as per IS 1641

Key Definitions:

• Fire Load (Q): Heat energy (kcal) released per m² floor area by combustion of contents + combustible building parts.

Formula for Fire Load:

[ Q = \frac{\sum (W_i \times C_i)}{A} ] Where:

• ( W_i ) = Weight of combustible material (i) (kg)
• ( C_i ) = Calorific value of material (i) (kcal/kg)
• ( A ) = Floor area considered (m²)

Important Notes:

• Fire load is used for occupancy classification.
• Combustibles may not be uniformly distributed; local concentrations can cause higher localized hazards.
• Fire load should ideally consider the worst-case local concentration rather than average over entire floor.

Classification:

• IS 1641 classifies buildings based on occupancy and associated fire load (details in Clause 3).

Practical Guidance:

• Use known calorific values from fire protection handbooks or standards.
• Assess fire load for each compartment or room, not just whole building.
• Consider fire load density (kcal/m²) for fire resistance design and hazard mitigation.

flowchart TD
    A[Combustible Materials] --> B[Calculate Weight (W_i)]
    B --> C[Multiply by Calorific Value (C_i)]
    C --> D[Sum all materials heat values]
    D --> E[Divide by Floor Area (A)]
    E --> F[Fire Load (Q) kcal/m²]
    F --> G[Use for Occupancy Classification & Fire Protection Design]

Summary:
Fire Load quantifies potential heat release per floor area and is critical for fire hazard classification and structural fire design per IS 1641.

IS 1641: Classification of Buildings Based on Occupancy

1. General Occupancy Groups (Clause 3.1)

• Group A: Residential
• Group B: Educational
• Group C: Institutional
• Group D: Assembly
• Group E: Business
• Group F: Mercantile
• Group G: Industrial
• Group H: Storage
• Group J: Hazardous

2. Group G - Industrial Buildings (Clause 3.1.1.7)

• Includes factories, labs, power plants, laundries, refineries, etc.
• Hazard depends on fire spread, smoke, explosion risks.
• Classification governed by highest hazard in building unless segregated.

Subdivisions:

3. Group A - Residential Buildings (Clause 3.1.1.1)

Note: Hazard classification affects fire safety design, material selection, and protection measures.

graph TD
  A[Building Occupancy] -->|Residential| A1(A-1 Lodging)
  A --> A2(A-2 Private Dwelling)
  A --> A3(A-3 Dormitories)
  A --> A4(A-4 Apartments)
  A --> A5(A-5 Hotels)
  A --> B(Educational)
  A --> C(Institutional)
  A --> G(Industrial)
  G -->

IS 1641: Fire Zones — Key Points on Number, Designation, and Demarcation

1. Demarcation of Fire Zones (Clause 4.1)

• The city/area is divided into distinct Fire Zones based on:
  • Fire hazard inherent in buildings/structures.
  • Occupancy classification (refer IS 1641 Clause 3).
• Purpose: To manage fire safety measures effectively.

2. Number and Designation of Fire Zones (Clause 4.2 & 4.2.1)

• Number depends on:
  • Existing city layout.
  • Types of building construction.
  • Occupancy classification.
  • Future development plans.
• Typical practice:
  • Large cities/areas: 3 Fire Zones.
  • Smaller cities/areas: 1 or 2 Fire Zones.
• Zones are designated based on fire hazard severity and occupancy risk.

3. Overlapping Fire Zones (Clause 4.4)

• Zones may overlap due to mixed occupancies or transitional areas.
• Overlapping zones require combined fire safety strategies.

Summary Table: Fire Zones by City Size

Conceptual Diagram

flowchart LR
    A[City/Area] --> B[Assess Layout & Building Types]
    B --> C[Classify Occupancy & Fire Hazard]
    C --> D[Demarcate Fire Zones]
    D --> E{City Size?}
    E -->|Large| F[3 Fire Zones]
    E -->|Small/Medium| G[1 or 2 Fire Zones]
    F & G --> H[Apply Fire Safety Measures]

Note: For detailed occupancy classifications and fire hazard criteria, refer to IS 1641 Clause 3 and related tables.

IS 1641: Demarcation of Fire Zones — Key Points

1. Definition (Clause 4.1)

• The city/area is divided into distinct Fire Zones based on the fire hazard level of buildings/structures.
• Classification depends on occupancy type (refer Clause 3 for occupancy classification).

2. Number and Designation (Clause 4.2)

• Fire Zones are numbered and designated according to the inherent fire hazard.
• Typically, zones are categorized as:
  • High hazard
  • Moderate hazard
  • Low hazard

3. Change in Boundaries (Clause 4.3)

• Any change in Fire Zone boundaries or inclusion of new occupancies must follow the formal procedure for promulgating new rules.

4. Overlapping Zones (Clause 4.4)

• Where Fire Zones overlap, the stricter fire safety requirements apply.

Typical Fire Zone Classification Table (Example)

Summary Diagram

flowchart LR
    A[City/Area] --> B[Fire Zone 1: High Hazard]
    A --> C[Fire Zone 2: Moderate Hazard]
    A --> D[Fire Zone 3: Low Hazard]
    B --> E[Strict Fire Safety Rules]
    C --> F[Moderate Fire Safety Rules]
    D --> G[Basic Fire Safety Rules]

For detailed occupancy classification and fire hazard ratings, refer to Clause 3 of IS 1641.

IS 1641: Number and Designation of Fire Zones (Clause 4.2)

• Fire Zone No. 1 (Clause 4.2.2.1) includes:

  • Residential buildings (Group A)
  • Educational buildings (Group B)
  • Institutional buildings (Group C)
  • Assembly buildings (Group D)
  • Small business (Subdivision E-1)
  • Retail mercantile buildings (Group F)
  • Areas under development for above occupancies

• Fire Zone No. 2 (Clause 4.2.2.2) includes:

  • Business buildings (Subdivisions E-2 and E-3)
  • Industrial buildings (Subdivisions G-1 and G-2)
  • Excludes high hazard industrial buildings (Subdivision G-3)
  • Areas under development for above occupancies

• Overlapping Fire Zones (Clause 4.4):

  • Where different fire zones adjoin or overlap, the more stringent fire protection requirements apply.

Summary Table

This classification helps in applying appropriate fire safety measures as per occupancy risk.

IS 1641: Change in Fire Zone Boundaries (Clause 4.3)

• Procedure for Change: Any change in fire zone boundaries or inclusion of new occupancies must follow the same procedure as promulgating new fire zone rules. This ensures consistency and safety compliance.

• Key Points:

  • Fire zones are designated based on occupancy types and hazard levels (see Clause 4.2 & 4.2.2.2).
  • Changes require formal approval and reassessment of risk.
  • Overlapping zones (Clause 4.4) must be carefully managed to avoid conflicts.

Fire Zone No. 2 Example (Clause 4.2.2.2)

Summary Flow for Changing Fire Zone Boundaries

flowchart TD
    A[Identify Change in Boundary] --> B[Review Occupancy Types]
    B --> C{Is it a new occupancy?}
    C -->|Yes| D[Follow New Rule Promulgation Procedure]
    C -->|No| E[Assess Overlapping Zones]
    E --> F[Formal Approval & Documentation]
    D --> F
    F --> G[Update Fire Zone Maps & Records]

Note: IS 1641 does not provide explicit formulas or tables for boundary changes but emphasizes procedural rigor and classification consistency.

IS 1641 Key Points on Overlapping Fire Zones & Temporary Buildings

Overlapping Fire Zones (Clause 4.4)

• Fire zones are designated based on fire risk and building use (Clause 4.2).
• Overlapping zones occur where two or more fire zones intersect.
• Design and fire safety measures must comply with the most stringent requirements of the overlapping zones.
• Ensure fire separation distances and fire-resisting construction as per the highest hazard zone.

Temporary Buildings (Clause 4.5.1)

• Allowed only in Fire Zones No. 1 and 2.
• Require a special permit from authorities.
• Use is for a limited period with specific conditions.
• Typically used for site offices, storage, or temporary accommodation.
• Must comply with fire safety norms relevant to their zone.

Summary Table:

Fire Separation Distance (Example)

Use the highest value if overlapping zones exist.

flowchart LR
    A[Fire Zones] --> B[Zone 1]
    A --> C[Zone 2]
    A --> D[Zone 3]
    B & C --> E[Overlapping Zone]
    E --> F[Follow stricter fire safety]
    B --> G[Temporary Buildings Allowed]
    C --> G
    D --> H[Temporary Buildings Not Allowed]

Note: Always consult local authority permits and IS 1641 for detailed conditions.

IS 1641: Regulations for Temporary Buildings

Key Points from IS 1641 (Clauses 4.4 to 4.6.3):

• Temporary Buildings (Clause 4.4): Allowed only with special permit from authority, for limited period.
• Fire Zones (Clause 4.5.1): Temporary buildings permitted only in Fire Zones No. 1 and 2.
• Construction Restrictions (Clause 4.6 & 4.6.3):
  • New buildings in Fire Zone No. 3 must be Type 1 or Type 2 construction (refer IS 1642-1988 for types).
  • Temporary buildings generally have restrictions on construction type to minimize fire risk.

Summary Table: Fire Zone vs Temporary Building Permission

Reference: Construction Types (from IS 1642-1988)

• Type 1: Fire-resistive construction (e.g., concrete, protected steel)
• Type 2: Non-combustible construction (e.g., steel, concrete without fire-resistive rating)
• Type 3 and below: Combustible or less fire-resistant materials (not allowed in Zone 3)

Practical Notes:

• Always obtain special permit for temporary buildings.
• Temporary buildings must comply with fire safety norms and time limits.
• Consult IS 1642-1988 for detailed construction specifications.

flowchart TD
    A[Temporary Building Proposal] --> B{Fire Zone?}
    B -->|Zone 1 or 2| C[Apply for Special Permit]
    B -->|Zone 3| D[Not Permitted or Must be Type 1/2 Construction]
    C --> E[Construct Temporary Building with Conditions]
    D --> F[Follow IS 1642-1988 for Construction Type]

For detailed design and fire safety compliance, refer to IS 1642-1988 and local fire authority guidelines.

IS 1641: Restrictions on Type of Construction for New Buildings (Clause 4.6)

The restrictions depend on the Fire Zone classification and refer to IS 1642-1988 for detailed construction types:

Key Notes:

• Type 1: Fire-resistive construction (most fire-resistant).
• Type 2: Non-combustible construction.
• Type 3: Combustible exterior walls but fire-resistive interior.
• Type 4: Heavy timber construction.

Summary:

• Higher fire risk zones require more fire-resistant construction types.
• Zone 3 (highest risk) allows only Type 1 or 2.
• Refer to IS 1642-1988 for detailed definitions and specifications of each construction type.

flowchart TD
    A[Fire Zone Classification] --> B{Zone 1}
    A --> C{Zone 2}
    A --> D{Zone 3}
    B --> E[Type 1, 2, 3, 4]
    C --> F[Type 1, 2, 3]
    D --> G[Type 1, 2]

For detailed fire safety design and material specifications, consult IS 1642-1988.

IS 1641: Compliance and Application Procedures - Key Points

• Rounding off results:
  As per IS 2:1960, all test or analysis results must be rounded off to the same number of significant figures as specified in IS 1641. This ensures consistency in compliance evaluation.

• Calorific values & hazardous materials:
  Detailed data on calorific values and hazardous materials are not included in IS 1641 but referenced from standard textbooks and the forthcoming Handbook on Fire Protection.

• Fire grading and classification:
  IS 1641 aligns with the Code of Practice for Fire Safety of Building (General) for principles on fire grading and classification.

Practical Compliance Steps:

1. Perform tests/analysis as per IS 1641.
2. Round off results according to IS 2:1960 rules.
3. Compare rounded values with specified limits in IS 1641.
4. Refer to external resources for hazardous materials and calorific values.

IS 2:1960 Rounding Rule (Summary):

If you need specific formulas or tables for fire grading or material classification, refer to the Code of Practice for Fire Safety of Buildings or relevant IS codes.