The tilde is a sign of comparison (see page 136 of the Nemeth Code, where it is part of the list of signs and symbols of comparison), and so it must follow the rules for spacing of symbols of comparison, which are in §151:
[quote=]"A space must be left on either side of a comparison symbol. However, a space must not be left between the comparison symbol and any punctuation symbol, grouping symbol, or indicator which applies to it."[/quote]
The "∆s" that follows the tilde in the example you give is a plural shape (see §39 of the NC) and is not part of the sign of comparison (tilde).