1.5W laser safety with effects lens

I know many people here are militant supporters of eye safety so I will begin by saying that I am not a moron and would never attempt to use a device even 1% this powerful without goggles. This question is purely out of curiosity since I have no idea what to expect and I'm sure others have wondered and hopefully tested this.

When it comes to a 1.5W blue laser with effects lenses, is it safe to use it indoors if you point it at a wall about 15-20ft away and every single beam of light coming out hits the wall and only the wall? I understand things go wrong and a beam may hit something else and reflect back here or there, but for the purpose of this question assume that every last beam will hit the wall.

I know just the focused beam alone is far too bright to be used indoors without protection, but I would like to see what the effects will look like indoors so long as its safe.

So has anyone ever tried this and is it too bright to safely view?

Thanks

The answer is usually safe don't have a big mirror in the middle etc and you will be fine, just be careful obviously no point in special effects if have to use googles i have a glass free room i use in my house and no pictures or metal only matt wood and other such matt items i use as a viewing room to be sure when letting rip with my blues ...