OSHA’s definition of a “mist” vs. science

“The term mist is applied to liquid suspended in the atmosphere. Mists are generated by liquids condensing from a vapor back to a liquid or by a liquid being dispersed by splashing or atomizing. Aerosols are also a form of a mist characterized by highly respirable [they mean breathed - respiration does not need lung in strict biological terms], minute liquid particles.”

First, the OSHA author confuses respiration with breathing. While the term "respiratory protection" is often used to refer to protective masks, respiration and breathing are not the same. Respiration is a biological function and it does not have to take place in a lung. Next, the word "minute" is vague and unscientific. While you can see a mist in the harbor and describe as such in standard prose, you need to be more accurate than that when it comes to describing whether a worker is being exposed to a mist in scientific terms. 

Ambient temperature, pressure, humidity of the air and the size of the particle in the mist as well as the composition of the material are all very important to determine how harmful the mist is and whether it qualifies as a mist.

Mists change as ambient temperature changes. A mist can be described generically as micron sized droplets that are suspended in air for a long period because they are not large enough or heavy enough to settle by gravity. Their size changes all the time. As temperature rises, the droplet evaporates and becomes a gas, so it disappears and may no longer be as noxious. As temperature drops particles may coalesce, like rain in clouds, making the mist disappear. For example, a mist of steam in a steam room could cause some people to cough because they are breathing in micron sized liquid droplets of water, which interfere with lungs function, like when a person drowns. However, when cold air is allowed in the room, water droplets coalesce and form large drops and fall to the floor or attach to walls. The air clears visibly. What remains is water vapor or humidity in the air, and no longer causes harm to the lungs. 

Some mists are so fine that they don't coalesce or settle easily and may remain in the air for a long time. These mists are often referred to as fogs. Foggers are used commercially to deliver insecticides. 

Definitions | Workplace Hazards

Q.	How has the definition of "asbestos" changed in the asbestos standards?
A.	The non-asbestiform varieties of the minerals actinolite, tremolite and anthophyllite are no longer included in the definition of asbestos.
Q.	Briefly, what are the four classes of activities covered in the Construction standard?
A.	"Class I" work is defined as activities involving the removal of thermal system insulation (TSI) and sprayed-on or troweled-on or otherwise applied surfacing asbestos-containing material or presumed asbestos-containing material. "Class II" asbestos work is defined as removal of ACM or PACM which is not TSI or surfacing ACM or PACM. Certain "incidental" roofing materials such as mastic, flashing and cements when they are still intact are excluded. "Class III" asbestos work is defined as repair and maintenance operations which are likely to disturb ACM or PACM. "Disturbance" means activities that disrupt the matrix of ACM or PACM, crumble or pulverize ACM or PACM, or generate visible debris from ACM or PACM. Operations may include drilling, abrading, cutting a hole, cable pulling, crawling through tunnels, or attics and spaces above the ceiling where asbestos is actively disturbed or asbestos-containing debris is actively disturbed. "Class IV" asbestos work means maintenance and custodial activities during which employees contact, but do not disturb ACM or PACM, and activities to clean up dust, waste, and debris resulting from Class I, II, and III activities. This may include dusting surfaces where ACM waste and debris and accompanying dust exists, and cleaning up loose ACM or PACM debris from thermal system insulation or surfacing ACM/PACM, following construction activity.
Q.	Do the new standards set a minimum level of asbestos content for asbestos-containing materials?
A.	Asbestos-containing material means any material containing more than 1% asbestos.
Q.	What is "presumed asbestos containing material" (PACM)?
A.	The definition of PACM is limited to thermal system insulation and sprayed on and/or troweled or otherwise applied surfacing material in buildings constructed no later than 1980. The material is "presumed" to contain asbestos unless it is demonstrated in accordance with the standard that PACM does not contain asbestos.

Q.	Does OSHA still use the term "small-scale, short-term"?
A.	No. OSHA has dropped the term "small-scale, short-term" work from the regulatory text. The term "small-scale, short-term" was too limiting, has been shown to be confusing, and could not be defined with sufficient precision to serve the purpose of distinguishing high risk asbestos-disturbing activity from activity of reduced risk.
Q.	Are "wrap and cut" operations included in the definition of "removal"?
A.	Yes, a wrap and cut operation is a type of asbestos removal. It consists of two distinct operations. The wrap portion requires the removal of small amounts of asbestos from either side of the pipe to be cut. This will be a Class I or III operation depending on the amount of asbestos removed. Once the asbestos is removed and wrapped, the pipe is then cut. The cutting portion of the job is unclassified, as it does not involve asbestos removal.