I had a big bust-up with Chris Boucher (by snail mail) over this episode - and over the lack of any scientific expertise or internal logic. This ended with me sending him a bar of soap to wash his mouth out with after Sand. (He had promised me that no-one would sentimentalise Servalan - who I think was one of the main problems with the later series, and who should have been used much more sparingly - on his watch.)