I highly recommend the use of an airfed face shield. The problem with turning is that it's dusty, and that's just the turning, sanding gets really dusty! I always say that the biggest danger to Woodturners, once you have learned to keep your bit of wood on the lathe, is the dust!
I used to use a powercap, which was good, and I used it for a number of years before the battery pack died. For about a year after that I used a disposable mask and face shield, believing the protection would be enough... Guess what? It isn't! I began suffering with Sinus issues so decided to bite the bullet and fork out for a decent system.
The best on the market is without a doubt the 3M but with a price tag in the region of £700 it is a bit of a stretch. I looked at the Trend but many reviews online reported the weight being an issue, and my stance does mean I tend to lean forward, putting strain on my neck. Protecting my lungs but straining my neck didn't seem like a good deal so I decided I wanted a belt mounted system.
I found the JSP Jetstream, which is the big brother of the powercap, costing around £400. It is built around a builders helmet so is lightweight, comfortable for long periods and also offers excellent protection against projectiles... Just in case!
The belt mounted power pack and carbon filter is where all the weight is and this sits comfortably on your waist/hips. The best thing about it is the level of filteration, it has a carbon filter which means you can't even smell the wood you are turning. If you can smell it, there must be something getting through!
I've had it for 2 years so far and really like it. It has an 8 hour battery so lasts a full long day of work without a problem. The only issue I have come up against is that there is an alarm which is designed to tell you when the filter needs changing/battery needs charging, which whistles and mine clearly has a fault as it whistles all the time but it doesn't bother me over the sound of my lathe and the radio.
HTH
Richard