Protect Workers’ Health with Dust & Fume Control

By: Divine Duruobioma, MSc, CMIOSH, Contributor

Dust and fumes in the workplace may pose significant health and safety risks. For instance, welding fumes containing metals like aluminum and lead can cause acute symptoms, such as nausea and/or long-term health problems (i.e., lung cancer).

Dust hazards vary by particle size; smaller particles, like respirable crystalline silica, can result in silicosis. Accumulated dust poses additional hazards, such as slips, fires (combustible dust) and equipment failures.

Dust consists of mechanically produced solid particles (e.g., grinding), while fumes are particles formed by condensation from gaseous states (e.g., welding). Key OSHA standards for control are found under 29 CFR 1910.94 and 1926.55.

Engineering controls are the best choice for minimizing employee exposures, as shown by the Hierarchy of Controls. When engineering controls are not an option, or while they are being implemented, respiratory protection might be required. (photo courtesy CDC/Niosh Website: About Hierarchy of Controls | Hierarchy of Controls | CDC)

Purpose of Dust and Fume Control

The purpose of dust and fume control is to protect workers’ health by minimizing exposure to airborne contaminants, thus reducing their health risks. Proper controls also enhance productivity and reduce potential liabilities associated with occupational injuries and illnesses.

Engineering controls are the best choice for minimizing employee exposures, as shown by the Hierarchy of Controls (see chart). When engineering controls are not an option, or while they are being implemented, respiratory protection might be required.

Implementing Control Measures

The primary purpose of local exhaust ventilation is to capture, transport and remove contaminants from the air before they reach workers’ breathing zones. To do this, let’s get an understanding of capture velocity and duct velocity.

What is Capture Velocity

Capture velocity refers to the speed at which air moves at the point of contaminant generation, which must be strong enough to pull dust or fumes into the ventilation system—before they disperse into the work environment. If the velocity is inadequate, contaminants may escape capture and pose a risk to workers.

High capture velocity (e.g., 100-200fpm for welding fumes) reduces exposure by 50-80%, ensuring contaminants are drawn into the system before dispersing into the workspace. Low capture velocity increases exposure by 2-10 times, due to contaminants escaping capture. For example, capturing velocities below 200fpm for wood dust can lead to hazardous exposure levels.

Involving employees in system selection and training on capture velocity and duct velocity promotes proper usage and maintenance. (photo courtesy Safex, Inc.)

What is Duct Velocity

Duct velocity is crucial for maintaining the effectiveness of a dust and fume control system, as it ensures that airborne particles remain suspended while being transported through the ducts. Inadequate duct velocity may cause particles to settle, leading to blockages and reduced efficiency; while excessive velocity can cause turbulence, resulting in reduced effectiveness, noise and vibration.

The ACGIH Industrial Ventilation Manual is one reference for typical duct velocities for various operations and contaminants. Optimal duct velocity (e.g., 3,500-4,000fpm for welding fumes) ensures efficient transport of contaminants and prevents blockages, keeping exposure consistently low and within OSHA limits.

Low duct velocity causes system inefficiency, leading to exposure spikes. Velocities below 2,500-3,000fpm can reduce system efficiency by 40-60%, increasing exposure to contaminants by 2-3 times the occupational limits.

Common Misunderstandings

Capture velocity is often confused with face velocity or duct velocity. It is critical to maintain the right capture velocity (the speed needed at the point of dust generation to pull contaminants into the system). Controls for metal grinding and dip tank vapors require different capture velocities, due to the varied contaminant characteristics, speed of contaminant generation and temperature.

Employee Involvement in Ventilation System Selection & Usage

Employee involvement is crucial to the success of ventilation systems. Workers are the first to encounter hazards and can provide valuable insight into contaminant generation, helping ensure the system meets workplace demands. Involving them in the system selection and training on capture velocity and duct velocity promotes proper usage and maintenance.

When employees understand how the system protects their health, they are more likely to follow procedures; spot issues early; and contribute to system upkeep—fostering a proactive safety culture and enhancing workplace hazard mitigation.

An effective control program would include the following elements:

1. Determine the Correct Capture and Duct Velocity
   • The particle size, shape and weight of the dust/fumes you’re controlling dictate the necessary capture and duct velocities.
   • Reference for typical industry standards (e.g., ACGIH’s Industrial Ventilation Manual).
2. Perform Regular System Maintenance
   • Inspect and clean ducts to prevent blockages.
   • Measure duct velocity with instruments (anemometers, manometers) to ensure consistent performance.
   • Maintaining the fan, including cleaning, lubrication and inspection for wear or damage, is also critical for sustaining adequate airflow.
   • A proactive maintenance plan minimizes downtime, enhances system longevity and ensures a safer work environment.
3. Train Employees
   • Train employees in the functionality of the ventilation system and how they must interact with it to maximize capture of generated contaminants.
   • Encourage employees to qualitatively assess the ventilation and report any unusual noises or decrease in effectiveness to maintenance.

An effective dust and fume control system requires understanding and applying the correct velocities at both the capture point and within the system to ensure proper containment and transport of contaminants. Continuous improvement through regular training and system evaluations is essential to maintain the effectiveness of control measures as workplace environments and hazards evolve. IHW

Divine Duruobioma, MSc, CMIOSH, Safex, Inc.

References:

1. American National Standards Institute & American Society of Safety Professionals. (2018). Fundamentals governing the design and operation of local exhaust ventilation systems (ANSI/ASSP Z9.2-2018). ANSI/ASSP.
2. American Conference of Governmental Industrial Hygienists. (2019). Industrial ventilation: A manual of recommended practice for design (30th ed.). ACGIH.
3. American Society of Heating, Refrigerating and Air-Conditioning Engineers. (2019). Ventilation for acceptable indoor air quality (ANSI/ASHRAE Standard 62.1-2019). ASHRAE.
4. Occupational Safety and Health Administration. (n.d.). Air contaminants (29 CFR 1910.1000). U.S. Department of Labor. https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000