Dust masks are a common sight at any worksite that involves significant amounts of dust or powder that workers could breathe in. While a dust mask is an essential piece of workplace safety equipment in such an environment, and is often the best available choice for the job, the masks are not without drawbacks.
Step One
Difficulty Breathing - A properly fitting dust mask forces the wearer to draw all (or nearly all) of their air through the mask in order to filter particulates out of it. The mask material is highly permeable, but does cause some resistance to the air flow, meaning the wearer has to breathe somewhat harder in order to draw a full breath at normal speed.
Step Two
Poor Fit - Dust masks are generally one-size-fits-all, and while they are made to conform to the shape of the wearer's face, their ability to do so is limited. This means that dust masks will often not quite fit right, digging in against the wearers' skin at some points and leaving gaps at others. This problem is amplified if the wearer has facial hair or an unusual face shape.
Step Three
Heat and Sweat - If your worksite is warm or involves physical labor, dust masks will exacerbate the effects of the heat involved. They form an insulating layer around wearers' faces, trapping excess heat and sweat, which can easily become quite uncomfortable.
Step Four
Limited Function - Dust masks cannot filter out all particulates in the air, and are completely ineffective against non-particulate hazards like gasses or vapors. If the air at the worksite contains anything more than simple dust or other large particulates, they can contribute to a false sense of security that could endanger their wearers.
Step Five
Covering the Face - Dust masks' basic function requires them to cover their wearers' nose and mouth. While this is necessary to prevent people from breathing in excess dust, it also makes it more of a hassle to eat or drink, since the wearers have to remove the masks (and expose themselves to the dust in the air) to do so. Covering the face also makes communication between wearers more difficult. The masks muffle their voices to a degree.