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The health hazards of dust
Respiratory system protection (through the use of masks), goes back almost two thousand years when a loose fitting animal bladder was used in the Roman mines to protect against the red oxide of lead. In the second century A.D., an improved respirator was developed which was a sackcloth added to the animal bladder, again for protection in mines.
In the fifteenth century, Leonardo da Vinci suggested the use of a wet cloth as protection against chemical warfare agents (which, at the time, hadn't even been developed). With the advent of the industrial revolution, great strides were made with the design and use of respirators. In 1814, a filter that removed particulates was encased in a rigid container that started the development of our modern day respirators.
The main problems encountered with all the early respirators were that they forced the wearer to breath in very hard. This, of course, was uncomfortable and didn't promote wide acceptance for these early crude devices. Studies on the principles of filtration by Robert Brown in 1827 produced filters that had less resistance to breathing and started the development lineage of our present-day respirators.
In 1854 the properties of activated charcoal were discovered in relation to the removal of organic vapors. Activated charcoal is still used today in respirators that are intended for use where organic vapors (stains, solvents, etc.) are present.
Rapid advancements in respirator technology were forced by the use of chemical warfare in World War I. This progress in design and filtration mostly concerned the ability to screen out highly toxic substances and do not pertain to the type of respirators in use today by woodworkers although improvements were made in the lift and comfort to where we now have the present day products. Throughout man's history, many people have worked in the search for respirator safety, yet many woodworkers don't use respirators because they don't realize the harm they can bring on themselves.
Respiratory System Basics
At its simplest, the body can be compared to a woodburning stove, or even a structured assembly of small stoves which are called cells. The fuel burned in our "stoves" is food taken in through our digestive tract in the form of sugar (glucose) and then delivered to the individual cells by the bloodstream.
The oxygen needed to burn this fuel is taken in by the respiratory system and transferred to the bloodstream to travel with the glucose to the individual "stoves". Of concern in this discussion of dust is how the air that is taken in reaches the bloodstream. Simplified, air is taken in through the mouth and nose into a single airway that separates into many smaller passages that end in the lungs.
In the lungs, the air passes through continously smaller passageways until it reaches the extremely small sacs called alveoli, of which there are approximately 300 million. These alveoli are separated by a very thin membrane, the alveolar wall, and which is permeable to gas molecules. It is here that the oxygen passes into the bloodstream and that carbon dioxide is removed.
This membrane is quite large (70-100 square meters) because of the body's inability to store oxygen as it can with water and fuel (in the fatty tissues). Man can live for weeks without food and days without water, but for only minutes without oxygen.
To see how all of this relates to your workshop, please read this article.
