Commercial Building Codes & Safety Guide

Hazard Classification (Low, Ordinary, High) and Hazardous Areas (NFPA 101)

Different types of building contents representing low, ordinary, and high hazard classifications

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The hazard of contents is a fundamental concept in NFPA 101, the Life Safety Code. It determines many aspects of building design, including:

  • Construction type requirements.

  • Sprinkler system requirements.

  • Travel distance limits.

  • Fire extinguisher placement.

  • Separation requirements.

NFPA 101 classifies the hazard of contents into three categories:

  • Low Hazard

  • Ordinary Hazard

  • High Hazard

This guide explains each classification and the protection requirements for hazardous areas.

NFPA 101 code book open to the hazard classification section

Section 1: What Is Hazard of Contents? (NFPA 101, 6.2)

The hazard of contents is the classification of the materials and contents within a building based on their potential to contribute to a fire.

Hazard Level Definition
Low Hazard Contents are of such low combustibility that no self-propagating fire can occur.
Ordinary Hazard Contents are likely to burn with moderate rapidity or to give off a considerable volume of smoke.
High Hazard Contents are likely to burn with extreme rapidity or from which explosions are likely.

Diagram showing low, ordinary, and high hazard classifications with examples

Section 2: Examples of Each Hazard Classification

Hazard Level Examples
Low Hazard Church seating areas, corridors, office areas, dwelling units, toilet rooms, break rooms, patient rooms, hotel guest rooms, lobbies, dining room seating areas, meeting rooms, ballrooms (not used for exhibitions).
Ordinary Hazard Parking garages, kitchens, mechanical rooms, storage rooms, retail stores, warehouses, elevator machine rooms, electrical rooms, soiled utility rooms, clean utility rooms, laboratories (depending on amounts of flammable/combustible liquids), ballrooms used for exhibition purposes.
High Hazard Saw mills, plywood/particle board manufacturing, furniture upholstering using foam plastics, flammable liquid spraying, mobile home manufacturing.

Pro Tip: The hazard classification is based on the contents, not the building construction. A building can be constructed of non-combustible materials but still have high hazard contents.

Examples of high hazard contents including flammable liquids and manufacturing

Section 3: Why Hazard Classification Matters

The hazard classification affects many aspects of building design:

Design Element Impact of Hazard Classification
Construction Type Higher hazard may require more fire-resistant construction.
Sprinkler Requirements Higher hazard may require sprinklers.
Travel Distance Higher hazard often has shorter travel distance limits.
Fire Extinguisher Placement Higher hazard may require more extinguishers.
Separation Requirements Higher hazard may require separation from other areas.
Means of Egress Higher hazard may require additional exits.

Sprinkler system in a high-hazard storage area

Section 4: Hazardous Areas Protection (NFPA 101, 8.7)

Hazardous areas are specific spaces within a building that contain materials or equipment with a higher fire risk. These include:

  • Boiler rooms

  • Mechanical rooms

  • Electrical rooms

  • Kitchens

  • Laundries

  • Storage rooms

  • Laboratories

Protection Requirements for Hazardous Areas:

Occupancy Type Requirement Code Reference
Ambulatory 1-hour rated wall assembly and sprinkler system; doors shall be self-closing. 20.3.2, 38.3.2, 9.2.3
Business (Sprinklered) 1-hour rated wall assembly and sprinkler system; kitchen shall be protected as per NFPA 96. 38.3.2.1, 8.7.1
Healthcare 1-hour rated wall assembly and sprinkler system. Table 18.3.2.1, 8.7.1
Educational 1-hour rated wall assembly or sprinkler system; kitchen shall be protected as per NFPA 96. 14.3.2.1, 8.7
Hotels & Dormitories 1-hour rated wall assembly and sprinkler system. Table 28.3.2.2.2
Apartments 1-hour rated wall assembly and sprinkler system. Table 30.3.2.1.1
Mercantile 1-hour rated wall assembly and sprinkler system; kitchen shall be protected as per NFPA 96. 36.3.2.1
Storage No requirements. 42.3.2

Hazardous area with 1-hour rated walls and self-closing door

Section 5: Special Considerations

Kitchen Protection (NFPA 96):

Commercial kitchens must be protected in accordance with NFPA 96 (Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations).

Electrical Rooms (NFPA 13):

Sprinklers are not required in electrical equipment rooms where all of the following conditions are met (NFPA 13, 8.15.10.3):

Condition Details
1. Dedicated to electrical equipment only. Only dry-type electrical equipment is used.
2. Equipment is installed in a 2-hour fire-rated enclosure. Including protection for penetrations.
3. No combustible storage is permitted. —

Electrical room with 2-hour fire-rated enclosure

Section 6: Common Mistakes and How to Avoid Them

Mistake Why It’s a Problem How to Fix
Misclassifying the hazard Applies the wrong requirements. Carefully classify the hazard of contents.
Not protecting hazardous areas Fire can spread from hazardous areas. Ensure hazardous areas are properly separated.
Not providing self-closing doors Fire can spread through open doors. Ensure all hazardous area doors are self-closing.
Ignoring occupancy-specific requirements Different occupancies have different requirements. Always check the specific occupancy chapter.
Not verifying with AHJ Local amendments may differ. Always confirm with your local Authority Having Jurisdiction.

Section 7: Quick Reference – Hazard Classification

Hazard Level Definition Examples
Low No self-propagating fire can occur. Offices, corridors, hotel guest rooms.
Ordinary Burns with moderate rapidity or gives off considerable smoke. Kitchens, retail stores, warehouses.
High Burns with extreme rapidity or explosions are likely. Manufacturing with flammable materials.

Conclusion

Understanding hazard classification is essential for designing safe, code-compliant buildings. By correctly classifying the hazard of contents and protecting hazardous areas, you can ensure the safety of occupants and property.

Take Action Today:

  1. Identify the hazard classification of all areas in your building.

  2. Check protection requirements for hazardous areas.

  3. Ensure self-closing doors are provided on hazardous areas.

  4. Verify with your local AHJ for any amendments.

Continue Reading from Our NFPA 101 Series:

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