Or worse you don't end up with mould/mildew indicating mould/mildew inhibiting chemicals have been added to the foam and are not pet safe.
There is a reason that all applications using this foam by experienced hobbyists with a penchant for creating their own habitats/decor items cover this stuff with pets safe (aquarium grade) silicone and/or pet safe paints and lacquers.
Don't get me wrong. Used correctly this stuff lives up to its' brand name. It is "great stuff" for the DIY crowd. It just pays to get into it with more thought than enthusiasm.