Below is a list of the common information that is communicated by recreational boaters using an air horn. The signals must be audible for at least one-half mile.
Note:
- A short blast = one second.
- A prolonged blast = 4–6 seconds.
Changing Direction:
- One short blast tells other boaters, “I intend to pass you on my left (port) side.”
- Two short blasts tell other boaters, “I intend to pass you on my right (starboard) side.”
- Three short blasts tell other boaters, “I am operating astern propulsion.” or “I am backing up.”
Restricted Visibility:
- One prolonged blast at intervals of not more than two minutes is the signal used by power-driven vessels when underway.
- One prolonged blast plus two short blasts at intervals of not more than two minutes is the signal used by sailing vessels.
Warning:
- One prolonged blast is a warning signal (for example, used when coming around a blind bend or exiting a slip).
- Five (or more) short, rapid blasts signal danger or signal that you do not understand or that you disagree with the other boater’s intentions.
