Hi @caxelby,
Thank you for your question about H3 treated pine.
These treatments allow the timber to be used in external applications where they are exposed to decay, fungus and pests. H3 pine, is usually treated with CCA (copper, chromium, arsenic), ACQ (alkaline copper quarternary) or LOSP (light organic solvent preservative).
The reality is, that if ingested, over time, any of these treatments can be harmful to your pet and awareness of this is important.
With this in mind, if sealed sufficiently and you ensure your dog does not chew the dog bed, there should be no issues. You can seal the timber with an external paint such as Dulux Weathershield Exterior Paint.
I wouldn't advise using stains as they tend to react poorly with the treatment in the timber and do not stay true to their colour.
If you are not ok with using the H3 pine, you can use untreated pine in the same way and seal it with an external paint, but you should be aware that it may rot quicker than H3 pine would.
You might like to have a look at How to choose the right timber for the job for some further information.
Let me know if you have any further questions.
Jacob
