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Case Study: Assessment of Dust Particles and Airborne Characteristics at a Training Facility

Case Study: Assessment of Dust Particles and Airborne Characteristics at a Training Facility

Sysco Environmental Ltd recently conducted a thorough assessment of dust exposure at a construction training facility focused on trades like carpentry and brickwork. This study aimed to understand the airborne characteristics of wood dust particles, such as their size, suspension time, and the risk of exposure to workers. In fields like carpentry, where dust is generated constantly, inhaling dust over long periods can lead to serious respiratory issues. By following COSHH (Control of Substances Hazardous to Health) guidelines, this assessment supports creating a safer, healthier working environment.
 
Tutors and apprentices working with softwood and hardwood produce varying sizes of dust particles during tasks like sawing, sanding, and assembling. Around 90% of the wood used in the carpentry area is softwood, while the remaining 10% is hardwood, creating a mix of airborne particles. These particles are categorised based on their aerodynamic properties, which affect their behaviour in the air and potential health risks. The key classifications are inhalable, thoracic, and respirable fractions.

Understanding Wood Dust Particles and Aerodynamic Characteristics


Wood dust particles vary in size and behaviour, which affects how they travel through the respiratory system:
 
- Inhalable Fraction: Particles under 100 microns in size that enter the nose and mouth. These larger particles are often trapped in the upper respiratory tract but can sometimes reach deeper, causing irritation.

- Thoracic Fraction: Particles under 30 microns that penetrate past the larynx and into the trachea and bronchi.

- Respirable Fraction: These are the smallest particles, under 10 microns, capable of reaching the alveoli in the lungs where gas exchange occurs. They pose the greatest risk for chronic respiratory conditions due to their deep penetration.
 

 Airborne Duration of Dust Particles


How long dust particles stay airborne depends on their size, density, and the surrounding environment, including air movement and ventilation. Generally, smaller particles stay airborne longer, while larger particles settle more quickly. Understanding this airborne duration helps assess inhalation risks, as longer suspension times increase the likelihood of worker exposure.
 

 Particle Size and Suspension Time


Respirable Particles (<10 microns): Small enough to reach deep into the lungs, these fine particles can remain airborne for extended periods—from minutes to several hours, depending on air movement. In still air, particles around 5 microns may stay suspended for up to 12 hours, while even smaller particles can linger almost indefinitely without active ventilation.

Inhalable Particles (10–100 microns): Larger particles generally settle faster, usually within seconds to minutes in still air. However, in spaces with high air movement, they can remain airborne longer.

Settling Speed and Air Movement: Larger particles, between 50–100 microns, typically settle within seconds to a minute in still air, while 10-micron particles can take up to 8 minutes. Active ventilation reduces suspension time and helps prevent dust build-up.
 
In a workplace setting where wood dust is constantly generated, good ventilation and dust control measures are essential. Without them, respirable particles—those most harmful to respiratory health—may stay airborne for hours, raising the risk of inhalation. Local exhaust ventilation (LEV) can play a significant role in reducing airborne dust duration by capturing particles near the source.

Sampling Methodology and Standards


The air sampling followed the Health and Safety Executive’s (HSE) MDHS 14/4 standard, a UK protocol for measuring inhalable and respirable dust. This assessment included both personal and static samplers to capture dust particles in the workers' breathing zones and background dust levels throughout the site.
 
- Personal Sampling: Sample pumps were placed within 0.3 metres of workers' breathing zones to capture real-time exposure during work shifts.

- Static Sampling: Monitors were set near high-dust equipment like chop saws and along key areas in the facility to gauge background dust dispersion.
 

 Health Risks of Wood Dust Exposure


Exposure to wood dust can have both immediate and long-term health effects:
 
- Acute Exposure: Symptoms can include eye and skin irritation, nasal dryness, and respiratory discomfort.

- Chronic Exposure: With repeated exposure to fine, respirable particles, risks increase for conditions like asthma, chronic bronchitis, and possibly COPD. Hardwood dust is classified as a carcinogen, heightening cancer risks with prolonged exposure.
 

Key Findings and Recommendations

 

Local Exhaust Ventilation (LEV) Effectiveness


   - Finding: LEV systems in the carpentry area, especially near high-dust tools, weren’t fully effective, with visible dust escaping and settling around equipment.

   - Recommendation: Enhance LEV systems with regular maintenance and add flexible hoses for targeted extraction. This will improve dust capture at the source, reducing airborne concentrations of both inhalable and respirable dust particles, and limiting how long particles stay suspended in the air.
 

Respiratory Protective Equipment (RPE)

   - Finding: RPE was available but inconsistently used, with no face-fit testing conducted.

   - Recommendation: Face-fit testing ensures that RPE fits correctly, especially important for high-dust activities. Designating RPE zones near carpentry equipment will reinforce RPE use in critical areas, providing consistent protection against airborne particles.
 

Housekeeping Practices

   - Finding: Dry sweeping was common in some areas, which re-suspends settled dust particles.

   - Recommendation: Switching to vacuum cleaning with HEPA filters or wet cleaning methods will prevent dust clouds from forming. If dry sweeping is necessary, RPE should be worn to reduce inhalation risks, especially in high-use areas.
 

 Conclusion

This assessment highlighted the complex risks posed by wood dust particles at the training facility. By improving LEV systems, enforcing RPE use, and upgrading cleaning practices, dust levels can be managed effectively. Additional measures like job rotation, health surveillance, and ongoing training will help reduce exposure to fine particles, ultimately supporting worker health and regulatory compliance. This approach aligns with COSHH guidelines, ensuring a safer workplace where respiratory health is prioritised.

OUR EXPERT

Tomas Gabor

0800 433 7914

Sysco Environmental Ltd provides expert industrial hygiene support to ensure safe working environments. Specialising in dust exposure assessments and control strategies, our team helps businesses implement best practices in Local Exhaust Ventilation, RPE usage, and health monitoring, creating safer workplaces and protecting employee respiratory health.

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