DHA Resources & Guides

Educational materials on NFPA 660 compliance, combustible dust hazards, and industry best practices.

📘 NFPA 660 Overview

NFPA 660: Standard for Combustible Dusts and Particulate Solids became effective December 6, 2024, consolidating all previous combustible dust standards into a single comprehensive document.

What NFPA 660 Replaces

Document Structure

Chapters 1-10: Fundamentals (all facilities)
Chapter 21: Agricultural & Food Processing
Chapter 22: Combustible Metals
Chapter 23: Sulfur
Chapter 24: Wood Processing
Chapter 25: Other Dusts & Particulates

Key Requirements

⚠️ Common Hazards & Remedies

These are historically common combustible dust hazards and their typical mitigation strategies.

🔥 Dust Accumulation on Elevated Surfaces

Dust settling on rafters, beams, pipes, and equipment creates secondary explosion fuel.

Remedies: Implement regular cleaning schedules. Use smooth, sloped surfaces. Install dust collection at source.

⚡ Static Electricity Discharge

Pneumatic conveying and material movement can generate static charges sufficient to ignite sensitive dusts.

Remedies: Comprehensive bonding and grounding program. Use conductive materials. Control humidity. Test MIE of materials.

🌡️ Hot Surfaces and Bearings

Overheated bearings and process equipment can exceed minimum ignition temperatures.

Remedies: Install bearing temperature monitoring with alarms. Preventive maintenance schedules. Keep equipment clean.

💨 Compressed Air Cleaning

Using compressed air disperses dust into suspension, creating explosive concentrations.

Remedies: Prohibit compressed air cleaning. Use approved vacuum equipment. Train all personnel on proper procedures.

🔧 Hot Work in Dusty Areas

Welding, cutting, and grinding near dust accumulations or where dust can become airborne.

Remedies: Hot work permit system. Thorough cleaning before work (35 ft minimum). Fire watch during and after.

🏭 Dust Collector Explosions

Dust collectors concentrate combustible material and can experience deflagrations.

Remedies: Install explosion venting (NFPA 68) or suppression. Spark detection upstream. Explosion isolation.

🔗 Interconnected Equipment

Ductwork and conveyors can propagate explosions between equipment.

Remedies: Install explosion isolation devices. Design systems with deflagration isolation. Regular maintenance and testing.

👁️ Hidden Dust Accumulations

Dust above drop ceilings, inside walls, on cable trays, and other hidden areas.

Remedies: Include hidden areas in inspections. Seal penetrations. Consider inspection ports. Document conditions.

🧪 Dust Testing Requirements

NFPA 660 requires testing or representative data to characterize combustible dust properties.

Test Standard Property Purpose
Go/No-Go Screening ASTM E1226 Combustibility Determine if dust is combustible
Explosion Severity ASTM E1226 Kst, Pmax Design explosion protection systems
Minimum Ignition Energy ASTM E2019 MIE Static electricity/spark hazard assessment
Minimum Ignition Temp (Cloud) ASTM E1491 MIT Cloud Hot surface ignition hazard
Minimum Ignition Temp (Layer) ASTM E2021 MIT Layer Dust layer ignition on hot surfaces
Minimum Explosive Concentration ASTM E1515 MEC Determine LEL for dust clouds
Limiting Oxygen Concentration ASTM E2931 LOC Inerting system design

Kst Classification

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