Know Your Combustible Dust

Get answers about your combustible dust and NFPA 652 compliance

Download our 2016 FAQ

Notable Combustible Dust Explosions

No industry is immune to combusitble dust explosions.

Determine Your Electrical Area Classification

Classes and Divisions

Equipment used in areas where there is concentrations of dusts exist must be equiped with special wiring and equipment to meet safety requirements. In order to use the correct equipment, the equipment has been divided into classes and divisions to match to the hazard identified in that area.

Class II, Division I

Where combustible dust is in the air under normal operating conditions in quantities sufficient to produce explosive or ignitable mixtures OR where mechanical failure or abnormal operation might cause explosive or ignitable mixtures and might provide a source of ignition through failure of electrical equipment

Class II, Division II

Where combustible dust due to abnormal operations may be present in the air in quantities sufficient to produce explosive or ignitable mixtures OR where combustible dust accumulations are present but are normally insufficient to interfere with normal operation of electrical equipment, but could as result of infrequent malfunctioning of equipment become suspended in air OR where combustible dust accumulations on, in, or in vicinity of electrical equipment could be sufficient to interfere with safe dissipation of heat from electrical equipment, or could be ignitable by abnormal operation or failure of electrical equipment


These areas have been broken down into specific groups that relates to the type of dust identified

Area Group Combustible Dust Material
Class II, Division 1 E Metal including magnesium, aluminum, titanium
Class II, Division 2 F Carbon dusts including carbon, coal and charcoal
Class II, Division 2 G Other non-conductive dusts including flour, wood & plastic

Have questions? Ask our experts

Definitions You Need To Know


Kst, the dust deflagration index, measures the relative explosion severity compared to other dusts. The larger the value for Kst the more severe the explosion. Different dusts of the same chemical material can have different ignitability and explosibility characteristics, depending upon physical characteristics such as particle size, shape, and moisture content. These physical characteristics can change during manufacturing, use or while the material is being processed. Any combustible dust with a Kst value greater than zero can be subject to dust deflagration.


Pmax is the maximum pressure of a dust cloud explosion


MIE is the minimum ignition energy, which predicts the ease and likelihood of ignition of a dispersed dust cloud.


MEC is the the minimum explosible concentration, which measures the minimum amount of dust dispersed in air required to spread an explosion.

No other event can cause as much damage to your facility as a combustible dust fire, deflagration or explosion

Still have questions? Request a quote to get answers!

Lewellyn Technology Combustible Dust Services

Dust Hazard Analysis

The purpose of the DHA is to identity hazards in the process and document how those hazards are being managed. Lewellyn Technology's industry professionals are well-versed in regulatory and standards, including OSHA and NFPA.


Your dust is unique and must be tested accurately in order to identify your hazard. Our professionals design a sampling strategy, recommend and analyze the right number of tests required. Our goal is always help you keep costs low and we look for the minimal number of tests required. Upon delivery of test results, Lewellyn will schedule a conference call with your site leadership personnel to discuss the testing results.

Engineering Controls

Data produced through testing and the DHA is used to properly engineer and protect your dust handling and processing equipment. Our team will work with you to develop a customized Basis of Design for specific projects. We provide guidance in preparing engineering documents to assist your engineers in establishing proper specifications for your equipment and systems, relating to combustible dust.

Administrative Controls

All engineered systems require administrative protocols to keep them up to date. Administrative controls such as Management of Change, Employee Training and Predictive & Preventive Maintenance are required by consensus standards, state and local codes.We work with your team to develop and implement robust administrative controls and integrate combustible dust compliance and risk mitigation into other safety management and compliance programs.

Electrical Area Classification

When electrical equipment is in operation around combustible dust, there is a risk of a fire or explosion. Our Electrical Area Classification determines the electrical classification as it pertains to combustible dust including Class II Division 1 or Division 2 hazardous locations for specific areas throughout your facility. Our experts will visit your facility to compare current operations and conditions and determine the appropriate electrical classification for the specified locations within the facility based off Federal OSHA Electrical Standards, NFPA 70 and ANSI/NEMA standards.

Dust Safety Programs

A comprehensive Combustible Dust Program for your facility provides a roadmap for adhering to applicable OSHA and NFPA combustible dust standards. Applicable standards include, but are not limited to the following: 29 CFR 1910.22, 29 CFR 1910.38, 29 CFR 1910.94, 29 CFR 1910.132, 29 CFR 1910.252, 29 CFR 1910.307, 29 CFR 1910.1200, NFPA 652, NFPA 654, NFPA 484, NFPA 68, NFPA 69, NFPA 77, NFPA 91, NFPA 499, NFPA 51B, NFPA 70, NFPA 101.