Industrial Hygiene (IH) Combustible Dust Sampling

What is IH Dust Sampling?

Industrial Hygiene (IH) refers to the process of identifying, evaluating, and controlling environmental stressors in the workplaces that may pose health risks to employees. A core component of IH is dust sampling, which involves measuring airborne particulate concentrations using calibrated personal sampling pumps and specialized filters worn by workers during typical operations.

Dust sampling helps determine whether employees are exposed to harmful levels of particulates and whether corrective actions are needed to comply with standards such as OSHA Permissible Exposure Limits (PELs). More details regarding general air sampling regulations can be found on SEC’s IH Air Sampling page. There are two primary categories of general dust monitoring:

1. 1. Respirable Dust – Fine particles capable of reaching the gas-exchange region of the lungs and measured using cyclone samplers or parallel particulate impactors
   2. Total Dust – All airborne dust particles, regardless of size, that can be collected using 37 mm cassettes with low-flow sampling pumps

What is IH Combustible Dust?

While many types of airborne dust present respiratory hazards, some pose an additional danger of combustibility. According to Occupational Safety and Health Administration (OSHA), combustible dust is defined as “solid material composed of distinct particles or pieces, regardless of size, shape, or chemical composition, which present a fire or deflagration hazard when suspended in air or another oxidizing medium.”

Combustible dust can manifest in three primary forms:

1. 1. Fire – ignition of settled dust or accumulations
   2. Flash Fire/Deflagration – rapid spread of flame through dispersed dust clouds
   3. Explosion – violent release of energy from ignition

Commonly regulated combustible dust categories include:

• • Food – flours, starches, sugars, powdered milk
  • Agriculture and grains – wheat, barley, oats
  • Metals – aluminum, iron, magnesium
  • Wood – sawdust and cellulosic dust (e.g. dust from paper)
  • Plastic – resin, polymer, copolymers
  • Chemicals – adipic acid, anthraquinone, dextrin
  • Carbonaceous materials – bituminous coal, subbituminous, lignite, charcoal
  • Other – textile, biosolids, soap, pet food

Identifying & Conducting IH Combustible Dust Sampling

Before sampling begins, IH professionals must evaluate whether combustible dust is present. Key indicators include:

• • Visual accumulations on flat or overhead surfaces
  • Improper housekeeping practices (e.g. compressed air to clean surfaces)
  • Indoor or outdoor dust collection systems operating without explosion protection systems or deflagration isolation
  • Unprotected duct or hopper discharges where dust can propagate
  • Repetitive exposure points and poor maintenance records
  • Etc.

Once potential risk for combustible dust is identified, IH sampling methods are used to measure airborne dust concentration and assess inhalation risk. While Dust Hazard Analysis (DHA) focuses on explosion potential, IH combustible dust sampling focuses on worker inhalation risk during normal operations. The general IH combustible dust sampling process follows:

1. 1. Dust Identification & Classification
   2. Particle Size Analysis
   3. Dust Concentration Measurement
   4. Oxygen availability
   5. Assessment of Workplace Conditions, including:
      1. Moisture Content
      2. Oxygen Availability
      3. Ignition Sources
      4. Dust Cloud Potential
   6. Facility Inspections, including:
      1. Housekeeping Conditions
      2. Combustible Dust Equipment
      3. Electrical Classifications – Identify Class II, Division 1 & 2 areas
   7. Review of Historical Dust-Related Incidents
   8. Conducting Safety Measures

Interpreting IH Combustible Dust Sampling Results

The results of IH combustible dust sampling can fall into several categories, each with unique implications for worker safety and compliance:

1. 1. Noncombustible Dust
      1. No fire/explosion risk
      2. May still present a health hazard depending on particle content
   2. Combustible Dust with Low Hazard Potential
      1. High autoignition temperatures
      2. High minimum ignition energy (MIE)
      3. Low likelihood of hazardous exposure
   3. Combustible Dust with Moderate Hazard Potential
      1. Lower ignition thresholds
      2. May require localized controls or exposure management
   4. Highly Combustible Dust
      1. Low ignition energy
      2. High explosibility and maximum deflagration pressure
      3. Requires urgent action and cross-evaluation with DHA
   5. Uncertain or Out-of-Spec Results
      1. Inconclusive or outside safety standards
      2. May require resampling or third-party lab verification

Based on your facility’s results, our SEC experts can provide tailored recommendations and compliance strategies.

Control Measures for IH Combustible Dust

There are several types of control measures for risk reduction, and applying the Hierarchy of Controls, the classifications are:

1. 1. Personal Protective Equipment (PPE)
      1. N95 or P100 respirators
   2. Administrative Controls
      1. Exposure time limits
      2. Job rotation to minimize individual dose
   3. Engineering Controls
      1. Local exhaust ventilation (LEV)
      2. Enclosed systems for dust-generating operations
      3. Filtration and dust suppression systems
   4. Substitution
      1. Replace hazardous materials with safer alternatives
   5. Elimination
      1. Redesign or automate tasks to eliminate dust generation
   6. Additional Measures
      1. Routine housekeeping and recordkeeping
      2. Filter maintenance
      3. Exposure trend analysis
      4. Audit preparedness

Recognizing and implementing the right exposure control measures is essential for protecting workers’ health and maintaining regulatory compliance. Our SEC team is here to help you assess risks, interpret results, and apply effective solutions tailored to your facility.