Apple's MacBook Air EFI firmware update 2.9 targets problems seen on mid-2011 models running OS X 10.9.2 and later.
The release notes say EFI version 2.9 fixes an issue that causes some systems to take longer than expected to wake from sleep. Also addressed is a rare issue that could cause system cooling fans to run at full speed after waking from sleep.
Apple notes the update should only be installed over EFI versions 0077.00, 0077.08, 0077.0E and 0077.0F on OS X 10.9.2 or higher.
The latest MacBook Air EFI update version 2.9 comes in at 4.3MB and can be downloaded via Apple's Support webpage or Software Update.