Dust vs. Respirable Dust
There’s a difference between the dust you can see when polishing a concrete floor and respirable dust you can’t see with the naked eye. The concrete dust you can see contains the larger particles of sand and process materials, and these materials contain crystalline silica churned up during the polishing process. Contained within that visible dust is potentially also respirable dust – which is dust that’s been pulverized down to less than 10 microns across, which is 100 times smaller than a single grain of ordinary beach sand. That’s the stuff you don’t want to breathe and that’s what’s being regulated by the new OSHA rules.
What’s Covered Under the New Rules
There are two basic types of silica: amorphous and crystalline. Amorphous, also called “free-flowing,” has a glassy non-uniform structure and is not regulated under this new standard. Crystalline, on the other hand, is a hard mineral where the silicon and oxygen molecules are held together in a uniform, lattice-like pattern. The problem occurs when the bonds holding the crystalline silica together are broken through grinding, sawing, pulverizing, cutting, sand blasting and jackhammering of everything from concrete and CMU to mortar and grout, sand, terrazzo and natural stone, and respirable crystalline silica dust is formed.
How Much Is Too Much?
OSHA has set the permissible exposure level of respirable crystalline silica dust at 50 micro grams per cubic meter (ug/m3) of air averaged over an 8-hour day. How much is that? Visualize a U.S. penny and imagine a pile of dust that would just cover Abraham Lincoln’s forehead. That’s the average amount of respirable dust to which an employee is allowed to be exposed during an average workday.
So, uhhh... What do I do?
Since the new respirable dust standards will apply to most people in the construction industry, OSHA has created Table 1, which lists 18 common tasks with a corresponding tool they feel is the best way to control dust in that situation. That takes the guess work out of a contractor’s job by saying, in effect, here’s your task and here’s your tool for controlling dust. And if you use those controls as listed on Table 1, you are exempted from the requirement to conduct air monitoring for that task, as well as being required to achieve the PEL of 50 micrograms per cubic meter of air (ug/m3) over an eight-hour day. However, you must implement those controls the way OSHA specifies, and it is important to note that these controls could require the use of respiratory protection. If you wanted to find out more about the new rules, Table 1 should be the first place you go.
For further study
PROSOCO has gathered some great resources to make sure you are up to speed on the new standards including Hilarie's full presentation as well as some awesome FAQs, useful links, and helpful resources for small businesses. Download them here.