Is there any replacement for ethyl mercaptan in LPG? Ethanethiol, commonly known as ethyl mercaptan, is a colorless gas added to LPG in order to detect its leakage.

Apart from ethyl mercaptan, is there any gas or liquid that may be used as a replacement to this?
Why would one want to replace it? 

The choice of ethanethiol is a reasonable compromise between its toxicity and the extremely low detection limit around 1 ppb (1mg/1000 kg).