NASCLA Accredited Commercial General ContractorMasonryHard
A masonry contractor is planning a project that requires cutting numerous concrete masonry units (CMUs) on-site. Which of the following safety precautions is most critical when operating a power saw for cutting CMUs?
- AOperating the saw at maximum RPM for faster cuts.
- BWearing only standard safety glasses, as full face shields are cumbersome.
- CEnsuring the cutting area is well-ventilated to prevent inhalation of silica dust.
- DUsing a dry-cut blade to minimize water exposure.
Show answer & explanationAnswer & explanation
Correct answer: C. Ensuring the cutting area is well-ventilated to prevent inhalation of silica dust.
Cutting CMUs generates significant amounts of respirable crystalline silica dust, which can cause severe lung diseases like silicosis. Therefore, ensuring adequate ventilation and using respiratory protection (like an N95 respirator or better) are critical to prevent inhalation.
Why the other options are wrong
- A. Operating at maximum RPM without proper technique or if the blade is not rated for it can be unsafe and lead to kickbacks or blade damage.
- B. While safety glasses are a minimum, a full face shield provides superior protection against flying debris, and respiratory protection is also crucial.
- D. Wet cutting methods are often preferred for CMU to suppress dust and cool the blade, making dry-cutting a less safe option for dust control.
Silica Dust Hazard
The risk of inhaling respirable crystalline silica (RCS) particles generated from cutting or grinding masonry materials, which can lead to incurable lung diseases like silicosis.
- Generated when cutting concrete, brick, stone.
- Causes silicosis, lung cancer, COPD.
- Requires engineering controls (ventilation, wet cutting).
- Requires administrative controls (work practices).
- Requires PPE (respirators - N95 or higher).
Memory trick: Dust is a silent killer; ventilate, wet, wear a mask.