Our 1960's house in California has aluminum wiring. When we bought it 15 years ago, I wanted the nicer Lutron receptacles and light switches, so I rewired all the outlets and switches using twist connectors + anti-oxidant paste + copper pigtails. I gather this is now not a recommended approach. We're selling the house and I don't want to leave a fire hazard, so I want to redo the work. The simplest and cheapest route is to replace receptacles and switches with CO/ALR rated ones, which I thought would be correct until I came across documents such as the CPSC guidelines that said this is not recommended, and that instead, using AlumiConn or Copalum connectors is the recommended approach. However, I also find discussions (on this site and elsewhere) where people say using direct aluminum wire connections to CO/ALR rated receptacles and switches is actually okay. Is it okay, or should I avoid CO/ALR devices in favor of the much more expensive and difficult route of using AlumiConn?
If your goal is safety, install AFCI breakers. The main failure mode of aluminum wire is arcing as a result of corrosion, and that's what AFCI breakers detect.
If your goal is compliance with a gold standard so you are lawsuit-proof, then CO-ALR receptacles will suffice. That's not my opinion, it's Underwriter's Laboratories. They listed these items as safe for use in that modality, as captured in the product's labeling and instructions, which are part of the listing. UL's testing presumes the end user will follow the instructions. NEC 2017 requires use of a torque screwdriver, so to complete the compliance, set torques correctly. Regardless, NEC permits CO-ALR, so clearly the NFPA agrees (that's National Fire Prevention Association).
All we have against them is CPSC's opinion, since they have not provided any provenance to whatever testing they have done if any. Certainly it would be more persuasive if they could point to some rate of house fires from CO-ALR failures. But all they say on the matter is "in real world conditions", which sounds to me like admission that they do work in spec conditions. Certainly the most likely place for installs to deviate from spec (especially homeowner installs) is torque.
CPSC is correct that not every connection type is available in CO-ALR. Here, enter the Alumiconn. A lug system whose lugs are, amusingly, made of aluminum.