It depends on the cleaning parameters. Bio cleaning temperature helps to reduce surface tension a little bit, but not a lot. The combination of spray pressure and the type of spray nozzles will decide whether its able to get into specific air pipe. In general, coherent nozzle with high spray pressure will help a lot. We have tested DI water cleaning on 25 mils gap height in our lab. It could still get in, but the cleaning rate is very slow and not able to meet costless product requirements.