Just thought I'd pop in to give my opinion here, as I've been looking into dust masks an awful lot and trying to choose the right one for myself.
I've tried the Trend Airshield and I must say it wasn't for me. I agree the protection is first class, it really does feel like breathing fresh clean air with no added strain in breathing as you try to pull air through a restrictive filter. The reason I personally wouldn't choose it is two things. One- although it avoided the sweatiness from an un-powered full face mask, the air movement directly around my face made my eyes water after an hour or so. Two- although the weight of the filter, motor and battery in the helmet is not massive, after a couple hours wear while looking down the increased weight starts to make my neck ache. At 6 foot 2 I also found that the opaque base of the face shield made me need to bend my neck further than usual to see things near my chest or at the near side of the workbench. Oh, another thing is the ear defenders you can add to the airshield are awful, and the bulk of the helmet makes wearing your own over the head types impossible, so you need to add either behind the neck defenders or in-ear plugs.
I've tried full face un-powered masks and the sweating in a warm workshop in the area around the eyes and forehead can get pretty impossible, since this area is totally sealed to air movement and therefore heat build up. The weight is better, and the visual obstruction is about the same. A positive thing was that the good filters are surprisingly easy to breathe through. I'd expected as much resistance as some of the cheap paper ones I've had in the past (I have lung problems and notice resistance really easily) but the decent 3m ones surprised me at how imperceptible they were.
Personally I've settled for a passive un-powered 3M half face mask and a plain cheap and open around the edges turner's visor. This gives me face protection, allows me to wear glasses and doesn't steam them up or make me sweat. I can still get dust in my eyes though, but I could, I guess easily enough wear goggles under the face shield/visor if I'm working on something spectacularly messy.
Obviously this is just my opinion, I'm even open to suggestions, but it's the best solution I've been able to find to the same question you seem to have.
Oh, and be warned, the replaceable filters on the 3m masks can still work out fairly expensive over time, a pack of them from axminster is about £50 so there's really no cheap option, just an option that's right for you.
And I'd suggest avoiding paper masks, they don't fit well, they're obstructive to your breathing, and altogether not very good at doing the job, just better than nothing.
Nic.