Class 3 flammable liquids are among the most commonly transported and stored hazardous materials worldwide. These substances are defined as liquids having a flash point of not more than 60°C (140°F) or any material in a liquid phase with a flash point at or above 37.8°C (100°F) that is intentionally heated and transported at or above its flash point in bulk packaging. 

The flash point is a critical measurement for classification, representing the minimum temperature at which a liquid gives off sufficient vapor to form an ignitable mixture with air near the surface of the liquid. This characteristic makes Class 3 substances particularly dangerous, as they can ignite at relatively low temperatures commonly encountered in workplace and transportation environments. 

 

Class 3 Flammable Liquid: Packing Groups and Classification 

Class 3 flammable liquids are further categorized into three packing groups based on their degree of danger, determined by flash point and boiling point characteristics: 

Packing Group  Initial Boiling Point  Flash Point  Examples 
 

Packing Group I (High Danger)      

  

Initial boiling point ≤ 35°C (95°F) 

  

Any flash point 

  

Diethyl ether, carbon disulfide, Crotonylene 
 

Packing Group II (Medium Danger) 

  

Initial boiling point > 35°C (95°F) 

  

Flash point < 23°C (73°F) 

  

Gasoline, acetone, methyl formate 
 

Packing Group III (Low Danger) 

  

Initial boiling point > 35°C (95°F) 

  

Flash point ≥ 23°C and ≤ 60°C (≥ 73°F and ≤ 140°F) 

  

Kerosene, diesel fuel, alcohols 

 

Common Examples 

Class 3 flammable liquids are widely used across various industries. Common examples include: 

  • Fuels: Gasoline, diesel, kerosene, aviation fuel, heating oil 
  • Solvents: Acetone, ethanol, methanol, benzene, toluene 
  • Industrial products: Paints, varnishes, lacquers, adhesives 
  • Personal care items: Perfumes, aftershaves, nail polish remover 
  • Cleaning agents: Various solvent-based cleaners 
  • Chemical intermediates: Petroleum ether, butanols, octanes 

 

Storage Requirements 

  1. Indoor Storage

Indoor storage of Class 3 flammable liquids requires specialized safety cabinets that meet strict construction standards: 

Construction Requirements: 

  • Double-walled sheet steel construction with a minimum 40mm gap between walls 
  • Liquid-tight spill containment sump at least 150mm deep 
  • Self-closing doors with proper sealing to prevent vapor escape 
  • Materials must not melt below 850°C 
  • Clear labeling: “FLAMMABLE – KEEP FIRE AWAY” 

Quantity Limitations: 

  • Maximum 60 gallons of Category 1, 2, or 3 flammable liquids per cabinet 
  • Maximum 25 gallons outside approved cabinets 
  • No more than three cabinets in a single storage area 

 

  1. Outdoor Storage

Outdoor storage facilities must meet additional requirements: 

  • Construction from masonry, concrete, or non-combustible materials 
  • Comprehensive spill containment systems 
  • Adequate natural or mechanical ventilation 
  • Proper separation from ignition sources (minimum 3 meters) 

 

  1. Ventilation Requirements

Proper ventilation is crucial for Class 3 flammable liquid storage to prevent vapor accumulation: 

Mechanical Ventilation: 

  • Minimum 6 air changes per hour for storage rooms 
  • Exhaust systems must vent to the outdoor atmosphere 
  • Air inlets at the top of the cabinet, exhaust from the bottom (vapors are heavier than air) 
  • Intrinsically safe exhaust fans are required 

Natural Ventilation: 

  • Acceptable for outdoor storage facilities 
  • Must ensure safe vapor dispersal away from ignition sources 

 

Transportation and Packaging 

Packaging Requirements 

Transportation packaging must comply with UN specifications based on the packing group: 

Packing Group I  Packing Group II  Packing Group III 
1. Inner packages: 0.5L maximum           capacity 

2. Outer packages: 66 lbs gross weight limit 

3. Forbidden for air transport 

 1. Inner packages: 1.0L maximum capacity (ground), 0.5L (air) 

2. Outer packages: 66 lbs gross weight limit 

3. Limited air transport allowed 

 1. Inner packages: 1.3L maximum capacity (ground), no limit (air) 

2. Outer packages: 66 lbs gross weight limit 

3. Most flexible transport options 

Labeling and Placarding 

All Class 3 shipments require proper hazard communication: 

  • Labels: Class 3 flammable liquid symbol with flame pictogram 
  • Placards: Required for shipments over 1,001 pounds 
  • Markings: UN identification number, proper shipping name, consignee information 
  • Special placards: “GASOLINE” may substitute for “FLAMMABLE” on fuel tanks 

 

Workplace Safety Measures 

1. Personal Protective Equipment (PPE) 

Workers handling Class 3 flammable liquids require appropriate PPE: 

  • Respiratory protection to prevent vapor inhalation 
  • Chemical-resistant gloves and clothing 
  • Safety glasses and face protection 
  • Non-sparking safety footwear 
  • Emergency eyewash and shower facilities are nearby 

2. Fire Prevention 

Critical fire prevention measures include: 

  • Elimination of ignition sources (minimum 3-meter separation) 
  • Proper electrical equipment rated for hazardous locations 
  • Grounding and bonding of containers and equipment 
  • No smoking policies in storage and handling areas 
  • Regular inspection and maintenance of equipment 

3. Spill Response 

Emergency response procedures must address: 

  • Immediate area isolation and personnel evacuation 
  • Elimination of ignition sources 
  • Proper cleanup using compatible absorbent materials 
  • Appropriate disposal of contaminated materials 
  • Environmental protection measures 

 

Emergency Response 

i) Initial Response 

First responders must follow established protocols: 

  • Approach from uphill and upwind positions 
  • Maintain safe distances using Emergency Response Guidebook recommendations 
  • Eliminate all ignition sources immediately 
  • Monitor air quality with appropriate detection equipment 
  • Establish an incident command structure 

 

ii) Fire Suppression 

Class 3 liquid fires require specialized suppression techniques: 

  • Foam-based suppression systems are most effective 
  • Water may spread liquid fires and should be used carefully 
  • Non-intervention may be preferred for large volume incidents 
  • Specialized training is required for railroad incidents involving flammable liquids 

 

iii) Health Hazards 

Exposure to Class 3 flammable liquids can cause: 

  • Respiratory irritation from vapor inhalation 
  • Dizziness, headaches, and nausea 
  • Skin and eye irritation from direct contact 
  • Potential organ damage from prolonged exposure 
  • Asphyxiation in poorly ventilated areas 

 

iv) Regulatory Framework 

Class 3 flammable liquids are regulated by multiple agencies: 

 

Transportation  Workplace Safety  Environmental 
  • DOT (Department of Transportation) – 49 CFR Parts 171-180 

 

  • IATA (International Air Transport Association) for air transport 

 

  • IMDG (International Maritime Dangerous Goods) for sea transport 

 

  • ADR (European Agreement) for road transport in Europe 
  • OSHA (Occupational Safety and Health Administration) – 29 CFR 1910.106 

 

  • NFPA (National Fire Protection Association) – NFPA 30 

 

  • Various state and local fire codes 
  • EPA regulations for environmental protection 

 

  • Spill reporting requirements 

 

  • Waste disposal regulations 

 

 

Conclusion 

Class 3 flammable liquids represent a significant hazard category requiring a comprehensive understanding and careful management. Their widespread use across industries necessitates strict adherence to storage, transportation, and handling requirements. Success in managing these materials depends on proper classification, appropriate storage facilities, adequate ventilation, comprehensive emergency planning, and ongoing training of personnel. Organizations must stay current with evolving regulations and maintain robust safety management systems to protect workers, the public, and the environment from the inherent risks associated with these volatile substances.