Alright, folks, let's talk respirators-for-1st-timers. Caveats: I don't have first-hand experience with this gear (I'm aggregating info), I will only be talking about 3M products (easy to find & reliable), and finding this gear in a pandemic is hard. That said... #seattleprotests

You need three things:
- a particle filter (for tear gas, which is a suspended powder)
- an organic vapor cartridge (to handle pepper spray)
- a mask to mount these on

There are several ways to get these things. Let's talk masks first.

You can get a full-face mask or a half-face mask. Full masks will keep your face from gas and spray, but may not be impact rated. Look on the masks for Z87+ to know that it's rated for impacts. Here's how to read the markings on protective eye-wear: https://www.graphicproducts.com/articles/ansi-z871-eye-protection/

I'd caution you towards an impact rated full-face mask or a half-face mask with impact-rated goggles. When buying goggles, look for D4 or D5 markings (D5 better). These indicate dust and fine dust protection. Tear gas is a dust. Choking on gas sucks. Losing an eye sucks more.

Now, for particle filters & OV cartridges. You'll have to pick one of three options: A combined filter & cartridge, separate "bayonet"-shaped filter and cartridge, or a bayonet-shaped cartridge and a round filter. This graphic shows the options: https://multimedia.3m.com/mws/media/279138O/3m-6000-7000-and-ff-400-series-respirator-technical-information-matrix.pdf

From last tweet's link, the 1st column are combined units. Part 60921 is a good combined for gas/spray. A 6001 (2nd column) + 5N11 (3rd) + 501 (3rd) is a good bayonet-shaped filter/cartridge option. 6001 (2nd) + 502 (3rd) + 2091 (4th) is a bayonet-shaped cartridge & round filter.

See how they fit together? All of these options are roughly equivalent (although the 5N11 is likely worse against tear gas due to being N95, not N100). They will all fit the same masks (look for "compatible with 6000-series cartridges"). So how do you pick?

With low availability, get what you can. If you can pick, avoid combined (60921); they're expensive to replace. 5N11 are very cheap, but less protection than 2091. If you can't find 501, they are 3d printable. If you don't care about pepper spray, 603 + 5N11 + 501 is cheapest.

All of this said, I'd love to hear from people with experience using more available, cheaper brands. Additionally, be aware that having gas protection will make you a target. Be prepared with a change of clothes for chest, crotch, feet being pepper sprayed. Keep safe out there!

Corrections, addendum, etc., to follow here!

Given that there's a pandemic on, avoid "CoolFlow" masks or any mask with a valve to let out air. It won't do "source control" (protecting other protesters from you if you have COVID).

Here's a link to some 3d printable 501 and 603 filter adapters: https://www.thingiverse.com/search?q=3m+501&type=things&sort=relevant