Respirators for Media Blasting

I've looked around this site and the web for recommendations on respirators for media blasting and there never seems to be any concrete information on what provides adequate protection. I understand there are liability reasons for this. For the ultimate protection, a fresh air supplied unit is a no-brainer. But short of that, for the hobbyist who can't afford to spend $500-$1000 on a fresh air system, there are little guidelines that I've found.
I know silica-based media releases nasty particles in the air and standard, particle dust masks will not protect against it. Beyond that, I've read info on NIOSH ratings and it's all clear as mud.
Does anyone know of any guidelines for what type of respirators will provide adeqaute protection for different types of media?
Also - Do walnut shell, glass and plastic media require the same protection as silica-based media?

maybe you can send a pm to donny,he would be our resident expert on what you need to know about media blasting and safety.

I can tell you that the dust from the broken down media and dust from paint just blasted off your parts is NOT anything you want to be breathing. See my avatar pic? That's the sort of Helmet/Hood you need, but, just this Nova3 Helmet system is $500.00 US dollars, you need an air filter system, and an air conditioning system too, you're at an easy $1500.00 for this stuff...and, the costs continue, trust me, Media blasting has a LOT of expenses.

you might check with your local body paint shops and automotive paint supply store and see if they have any used fresh air systems.
The systems have evolved over the years... we have old ones left over from updating the systems but worked just fine.
also Some jobs are best to just pay for by some one tooled up to do it correctly.
back in the day before we knew any better we would just suit up with an old pair of coveralls mask up sleeves and legs and a welding hood with a clear lens and go out back and go for it! not a good plan and what a mess dealing with all of the sand that went every where.

Other than supplied air, I don't know of anything better than HEPA.
But it's not rated for silica dust.
They probably are thinking inside use where concentrations are very high.

Folks, good intentions, however, all these are junk when you're media blasting. I can sell you a used Nova 2000 Helmet/Hood system, heck, I'll even toss in some tear off shields and inner shields too! PM me if you're interested.

Silica base materials are hazardous and as Donny stats a no no without proper equipment there are much safer media's out there for the due it yourself crowd that do a good job. Unless it will fit in a blast cabinet with a water base filter to trap all air born partiicals stay away from silica's. Your lungs will love you for it.