Recognize the signs. Difficult or impossible to remove. Normal acetone or acrylic solvents wont dissolve the material, making necessary the use of electric drills or extremely coarse files. An unusually powerful, noxious odor. Wearing a mask does nothing to prevent inhalation of MMA fumes.
Masks only reduce the inhalation of acrylic dust.
Low priced full sets and fills. While MMA monomer may cost less to buy than other products, the health risks are more costly in the long run. Understanding the chemistry. The chemical reaction that makes molecules link into long chains is called polymerization. While both EMA and MMA can also be found in acrylic powders, they are already polymerized and are formed into a new inert compound during the formation of the powder, which is non-reactive on your hand.