If you are a woodturner, you work in an environment where hazardous levels of dust are in the air you breathe.
Turning generates dust, and breathing dust is harmful to your health. It can cause breathing problems or cancer, and dust on the skin can lead to dermatitis. All types of wood dust are hazardous, including softwood dust.
The best way to avoid exposure would be to work in such a way that dust is not produced. Keeping tools sharp, using the less dusty timber species, and wet sanding with water or oil will help reduce dust levels. But most turners need a more effective way to protect themselves.
One obvious precaution is a breathing mask. It is the easiest and at its most basic is the least expensive option. A mask can be effective for low levels of exposure. It may be appropriate for people who do not turn frequently or for long periods of time, where the cost of dust extraction is not justified. But it is not the best primary protection for most turners. There are several reasons for this.
Although a well-fitting mask can protect the wearer, it can only do so while it is being worn. Hazardous dust is so fine that it remains suspended in the air for a long time after work stops. A mask must seal to your face to prevent unfiltered air being drawn under the edge, so may be uncomfortable to wear. If you take it off when the job is done, you will then be breathing air that is still dusty.
The best kind of n95 mask for sale is a powered unit that filters the air before blowing it over your face. These can be acceptable for hours of use, as the positive fan pressure means that the mask doesn’t have to seal to your face. In addition, the visor may be impact resistant.
A mask will not prevent dust from contacting your skin.
An air cleaner will filter the workshop air. They remove the dust, but have failings. Most importantly, the turner is closer to the dust source than is the air cleaner, so the inhaled air carries the heaviest load of dust. A cleaner takes a significant time to remove all the suspended dust in the shop. It is not just a question of comparing its rated air flow with the volume of the workspace. The filtered air mixes with the unfiltered air, and the dust concentration is reduced slowly. Meanwhile anyone in the workshop is breathing it in.
An air cleaner should be positioned so that it will set up a circulation of filtered air around the shop, but there are always likely to be dead spots where dust removal is slower.
Some people suggest just using a fan to blow the dust away from the turner. In the right conditions this could work. It will reduce the highest concentration in the inhaled air even if the dust remains in the workshop. If there is enough general ventilation in the shop, the concentration may never build up to harmful levels. But it is not a reliable method. The ventilation and the direction of air flow from the fan may vary, and harmful levels may be reached without you knowing.
A simple extractor fan in a window will not set up enough air flow to move the dust away from you.
A dust extractor should be positioned so it catches the dust right where it is generated and before it gets into the general air circulation of the workshop. This is in principle the best solution, and is the reason why workplace health legislation favours extraction over the other options. But not all extractors are suitable, because the lathe is a difficult machine to extract dust from.
The dust source may be anywhere along the lathe bed or across a spinning disc, and the particles are thrown in all directions, including towards you and away from the extraction inlet. Meanwhile, you are bending closely over the work and breathing in the highest concentration of dust. The suction has to overcome the speed of the air movement generated by the spinning work. Dust from the tool or from sanding will be entrained in this moving air, which may be quite rapid – you can feel the wind coming off the edge of a spinning disc.
This means that a powerful extractor is needed. Unfortunately, the suction from any extractor falls off very rapidly with distance from the inlet. At a distance equal to the diameter of the inlet, the air speed may be only about 10% of what it is in the mouth of the inlet. This is because the air is drawn into the inlet from all directions, including from behind it.
Therefore, to capture the dust the inlet diameter needs to be large, so the dust source can be within its effective zone; it must be adjustable so it can be positioned close to the dust source; and the extractor must be powerful enough to provide good air flow through the large inlet. It’s not enough just to use a large collecting hood if the extractor is too small for it.
It is important that the extractor has a fine filter, otherwise much of the dust will be returned to the workshop. With a fine filter, an extractor can act as an air cleaner if it is left running.
There are two kinds of extractor – high volume low vacuum; and low volume high vacuum, which are similar to domestic vacuum cleaners. Lathes need a high volume air flow to capture the dust, rather than high vacuum. There is an overlap between these types of machine, and some powerful high vacuum machines may be able to move more air than a small low vacuum one. It is important to check the cubic feet per minute specification and not be fooled by the high suction that you feel when you put your hand over the inlet. The vacuum will pull hard when the inlet is blocked, but comparatively little air may be moving through the pipe when it is open. These machines are very good when the dust source is enclosed and the pipe can be connected to the source, for example for power tools with a hose connection. But if they are used to extract from a lathe, the inlet must be positioned very close to the source, and moved as the source moves, which is not always practicable.
Whatever kind of extractor is used, it will often fail to get all the dust. A dust mask can then be used to supplement the extractor. Many turners routinely use both.