Iron Lungs

Iron Lungs is a CoD4 multiplayer Thrid Tier perk. It allows a player with a sniper scope to hold his breath for 9 seconds instead of 4. The downside is that if you hold it for this maximum time, it will take 10 seconds to get your breath back. This should be the perk of choce for most snipers if you don't use the ACOG. Most veteran snipers will not use it though as they can snipe players much easier. This perk is useless with all other guns and ACOG sniper rifles.