For those who want to use their Raspberry Pi 5 without a casing when it is operating at a high sustained load, there is an alternate cooling option available: the Official Raspberry Pi 5 Active Cooler. Using the same fan connector for power and control, it integrates a sizable metal heatsink and a variable-speed blower. It fastens to the Raspberry Pi 5 PCB using spring pins into two mounting holes.
Qualities:

Original Product: Raspberry Pi.
A temperature-controlled fan that can produce air flow of up to 1.4 CFM.
Air flow across the memory, processor, and power management integrated circuit.

One official Raspberry Pi 5 active cooler is included in the package.

Documents

https://datasheets.raspberrypi.com/rpi5/raspberry-pi-5-product-brief.pdf?_gl=1*up1v3a*_ga*MTc1NDIwNDguMTY5NTk3MjcyMA..*_ga_22FD70LWDS*MTY5NjAwNTc1MC4zLjEuMTY5NjAwNjM1Mi4wLjAuMA..