Plenty of good info in this thread.
I notice that these types of threads tend to have the same types of questions arise on a consistent basis.
The typical arrangement for nearly all negative pressure (naturally-aspirated) cartridge respirators is to have an intake port(s) and an exhaust port. One-way "flap" valves at each port allow the proper direction of airflow.
The exhaust valve opens only during exhalation, meaning that any inhaled air comes only through the filters. The intake valve(s) opens only during inhalation, ensuring reasonable filter cartridge life (if the design allowed both inhaling and exhaling through the filters, then filter life expectancy would be very low).
For those who are completely new to the idea of using a respirator, the first thing to realize is that no matter what type, brand, or expense of the apparatus, all is for naught if it is not sealed properly around your face.
There are several ways to check for proper sealing, but the most effective method is to tightly place the palm of your hand over the exhaust port of the respirator, then attempt to exhale. If the respirator is properly sealed, exhalation will require some effort. Of course, this assumes the one-way intake valves are in proper working order.
The respirator will want to bulge outwards away from your face as the exhaled air tries to find an escape route.
If it is properly sealed and you exhale with enough force, the seal will eventually break free from your face and the exhaled air escapes wherever the seal breaks. Most of the time this emits a sound similar to
flatulence (keeping in mind this is a G-rated forum, of course!).
Partial "half mask" or full-face? This is dependent upon both personal preference and working conditions, but something to consider is that most conditions hazardous to the lungs can also be hazardous to the eyes. For purposes of this discussion, the referred-to conditions would include particulate dusts such as metal, wood, etc.
For years, the use of prescription eyeglasses prevented me from using a full-face respirator. Several cases of noninfectious conjunctivitis and eventually a scarred cornea prompted me to find a better solution.
Contact lenses in combination with the full-face seemed to be the answer, but, in my case anyways, the confines of the respirator caused the contacts to quickly dry out.
Fortunately, the manufacturer offered an accessory for eyeglass wearers that holds a pair of lenses bridged between the nosepiece and top inside the faceshield.
If your personal preference, budget, or conditions (especially use of peripheal vision) favor a half mask (covers mouth and nose only), at least consider using safety goggles as a method of sealing the eyes.
What type of cartridges to use? Probably the question asked most frequently. Naturally, it depends on what it is you're trying to filter from the air you're breathing.
Knifemakers can expose themselves to all sorts of stuff that has long-term effects.
Our immediate concerns focus on the particulates such as wood dust, metal dust, abrasives, etc., as these seem to be the most obvious.
Depending upon production volumes, workshop conditions, and personal sensitivities, other items besides particulate dusts can also be a concern. Examples would be constant exposure to fumes, particularly epoxies. If you're the type who spends an entire day making several sets of "homemade micarta", you know what I'm talking about. For those who do a lot of machine work, having surrounding air constantly saturated by an oil mist can sometimes present problems.
Although it goes against my grain to recommend this particular manufacturer, 3M has a selection process to help narrow the selection:
http://solutions.3m.com/wps/portal/3M/en_US/Health/Safety/Resources/Four/
The most reliable source of accurate info is to go directly to those whose occupations require respirator usage. But the local GE plant probably isn't going to take you on a guided tour to learn about respirators.:biggrin:
A better solution for the average individual is to visit someplace like a local body shop and talk to the guys there.
Industrial supply houses are usually a good source, but the better ones are those who tend to specialize in safety equipment.
Finally, a dedicated paint supplier (Sherwin Williams, Porter, ICI, Benjamin Moore, etc.) will be
considerably more knowledgeable than the local hardware store/home center. One phone call or visit to the store telling them what you're working with, and they'll tell you exactly what you need.
Plus the fact that they have a direct link to the manufacturer. This is not to be overlooked, because it can save endless hours of research on the subject, and it allows them to obtain anything you need, rather than compromising for whatever happens to be on the shelf.
