Is the fan making noise? That would be a maintenance issue. Is the fan running fast a lot? That would be a heat issue. This could be caused by several things. Buy a can of compressed air, and blow out the air ducts. The CPU is being overworked.

Try: *https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix ---- You can try to disable hardware acceleration in Firefox. *Options/Preferences -> General: Performance<br>remove checkmark: [ ] "Use recommended performance settings"<br>remove checkmark: [ ] "Use hardware acceleration when available" *https://support.mozilla.org/en-US/kb/performance-settings Close and restart Firefox after modifying the setting to make the change effective. *https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems You can check if there is an update for your graphics display driver and check for hardware acceleration related issues. *https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration