What household compound will neutralize naphthalene-stained washer (for clothes)?
Napthalene is not water soluble, so the temperature doesn't matter as much as the detergent. What makes you think it's napthalene, though? It could be some organic compound in which case you need a good de-greaser (Dawn is the easiest to get, but there are better industrial ones like what cleaning crews may use). If what you're dealing with is an aromatic hydrocarbon (which napthalene is), airing it out will go a long way. I would see how far you can get with a fan blowing it out before you wash the rest out with a good de-greaser.