USAT (USA Triathlon)
Front-mounted snorkels and Powerbreather (symmetric) Snorkels are gaining popularity in swimming circles as training aids because they can help improve technique and lung capacity.
While technique training with a front mounted snorkel is very beneficial, training at any sort of distance or length of time is not recommended due to the mix of O2 and CO2 in the snorkel. Racing, adrenalines high, breathing fast at the start, only increases the effects of breathing mixed air. It's not efficient or effective and should not be done. The Powerbreather is a fresh air snorkel, we do not have this issue.
USA Triathlon, the governing body for the sport in the United States, snorkels are legal. As long as it does not provide a propulsion it is legal. USAT does ban artificial propulsion devices. These include, but are not limited to, gloves, fins, paddles and floating devices. Wetsuits cannot be thicker than 5 mm in any portion of the suit. The penalty for violating this rule is disqualification. Triathlon Australia and Triathlon Canada do not specifically ban snorkels, either. Same goes for the International Triathlon Union, which is the worldwide governing body for the Olympic triathlon.
That said, the race director has the final say as to what is allowed, so be sure to check with the race director before you show up at the race. And good advice... if you use a snorkel when you practice, do not do so exclusively because it may hamper your snorkel-free performance on race day.
While most Ironman athletes are known to train extensively with snorkels, and you'll see Powerbreather USA at Kona this year... Snorkels are specifically banned by the World Triathlon Corporation, which runs the Ironman series of races. WTC Ironman races generally follow rules set by USAT. However, WTC does request some dispensations from USAT, including the snorkel ban. WTC also bans fins, flotation devices and paddles. Wetsuits are prohibited in water that is 83.8 degrees Fahrenheit or warmer.
The British Triathlon Federation rules do not include snorkel use, so snorkels are therefore banned by omission. The only swimming aids allowed under British Triathlon rules are goggles, a cap, a nose clip and a costume such as a wetsuit. Gloves and socks cannot be part of the wetsuit “costume.”