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How long before H3 treated Pine loses smell?

MKHmn

Hi everyone,

I'm hoping to get some advice from those with experience using treated pine indoors.

About four weeks ago, I built a home theatre seating riser using H3 treated pine framing, insulation, plywood, and carpet. Since then, I've noticed a persistent chemical/petrol-like smell in the room. It's not a mouldy smell—it's more like fresh paint or treated timber.

The room is a dedicated home theatre, so it's relatively well sealed with limited natural ventilation. The smell is most noticeable when I first enter the room after it has been closed for a while. After spending some time in the room, I notice it less, but it's still concerning.

A few questions I was hoping someone could help with:

Is it normal for H3 treated pine to continue giving off this type of smell after four weeks?
During winter, does the off-gassing process take significantly longer?
Has anyone experienced something similar, and if so, how long did it take before the smell disappeared?
Is there anything practical I can do to speed up the process, other than increasing ventilation?
If the smell doesn't improve, is there a suitable low-VOC sealer or primer that can be applied to the timber (where accessible) to help lock in the odour?

I'd really appreciate any advice or shared experiences before I consider dismantling part of the riser.

Thanks in advance!

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R4addZ

Hi @MKHmn

The fumes from H3 treated pine can be hazardous. But the simple fix it to either paint or varnish it with oil based products to seal it. You should be using PPE and washing your hands after handling it!

MitchellMc

Welcome to the Bunnings Workshop community @MKHmn. It's wonderful to have you join us and many thanks for your question on treated pine.

I'm sorry to hear you're having this issue.

Unfortunately, H3-treated pine typically isn't intended for interior applications like a home theatre seating riser. H3 treatment is designed for above-ground external use, whereas H2-treated pine is the treatment level intended for interior framing applications. Because of this, many members won't have experienced what you're describing in an indoor environment.

Compared to H2-treated timber, H3-treated pine typically has a much stronger odour due to the preservatives used in the treatment process. In a well-sealed room with limited ventilation, those odours can be much more noticeable and may persist for longer than they would in an outdoor setting. Cooler winter temperatures may also slow the dissipation of any residual odours. Ventilating the room will help with the odour.

If the smell continues to be an issue despite improved ventilation, you may wish to consider whether replacing the H3 framing with a timber intended for interior use would be the most appropriate long-term solution.

Let me tag @SSyed to see if he has any thoughts.

Please let me know if you have any questions.

Mitchell

MKHmn

Thanks Mitchell

@ R4addZ That is not correct not with the new timber , I have contacted the company and there is no danger

Dave-1

Good Afternoon @MKHmn

I have a bench seat that sits outdoors (yeah not an enclosed space) but I have been using it constantly over the past two years and apart from fresh cut timber scent at first I have never smelt anything. I think I have a sensitive sense of smell. Time will solve it I would think.

Dave

MKHmn

Thanks Dave

Over the last two days, I left both doors open continuously and ran an industrial fan. The smell has improved significantly—I'd say it's about 50% better. However, if a guest walks into the theater, they would still notice the smell.

I've also placed activated charcoal in the room to help absorb the odour.

I'm simply looking for a solution to get rid of the smell completely.

R4addZ

@MKHmn

I said "can be" not is and sealing it as I suggested should take the smell away.

Edited to add

Fumes from H3 treated pine can be hazardous, particularly when the wood is freshly treated, burnt, or cut using power tools. The level of risk largely depends on the preservative used, how the timber is handled, and the environment it is placed in. [1, 2, 3, 4, 5]Types of H3 Treatments & Fume RisksIn Australia, H3 timber (used for outdoor above-ground applications) is primarily treated with three methods, each with different hazards: [1, 2, 3, 4]

LOSP (Light Organic Solvent Preservative): These timbers utilize organic solvents and insecticides (like Permethrin) to penetrate the wood. They have a noticeable chemical/solvent smell when fresh. [1, 2, 3]
Water-Based (ACQ or Copper Azole): These are arsenic- and chromium-free. Once dried, they do not off-gas or emit significant fumes, making them generally lower toxicity. [1]
CCA (Copper Chrome Arsenate): While mostly restricted from domestic high-contact uses, some older H3 fences or recycled stocks may still be CCA-treated. [1, 3, 4, 5]

Dave-1

Afternoon @MKHmn

Time :) time heals all and yeah @R4addZ suggestion of them being sealed works well.

Dave

MKHmn

I have contacted them and they inform me there is no risk tpaa , the general info from Google is not useful

R4addZ

@MKHmn

Try NSW EPA then

Click on the link and check out what it says about children! MitchellMc's suggestion of replacing it would seem the better option. No company will ever suggest their product has issues, they will just point you to safe handling and use advice it's then down to you.

Edited to add, At the end of the day, the choice is yours but bear in mind that you aren't supposed to burn treated pine because it then definitely does give off toxic fumes so hope you never have a house fire. Your choice of timber was unfortunately wrong and if it's just the smell you want rid of then paint or varnish it but since you are talking to the manufacturer ask them to send you an SDS (Safety Data Sheet) for the product and make your decision based on that.

Oh and when do we get pictures of your theatre, I'm sure others would like to see it.

MKHmn

In my case, the riser is fully enclosed and covered with thick plywood and carpet, so there is no direct contact with the treated timber. The only issue I'm trying to address is the remaining fresh paint/timber smell, which has already improved by around 50% after leaving both doors open for two days, running an industrial fan, and using activated charcoal. @ R4addZ

SSyed

Thanks @MitchellMc for looping me in.

Hi @MKHmn, nice to e-meet you.

What you're experiencing isn't uncommon, especially in winter and in a well-sealed room. If the framing was built using H3 treated pine, some residual treatment odour can linger for a number of weeks. H3 timber is generally intended for above-ground external applications under AS/NZS 1604, while H1 or H2 treated timber is more commonly used for internal framing.

I'd give it a little more time and increase ventilation where possible. If the odour doesn't improve and replacement becomes necessary, H2 treated pine or untreated structural pine would typically be more suitable options for an internal platform, subject to your DIY project requirements.

I hope the above is of assistance.

dammit

how’s the smell so far @MKHmn

JacobZ

Hi @dammit,

Welcome to the Bunnings Workshop community, it is fantastic to have you with us.

Hopefully @MKHmn will get back to you shortly.

If you had any questions or concerns that we can assist with, please don't hesitate to reach out.

Jacob

MKHmn

@JacobZ @ dammit

The smell is about 90% gone now. I only notice it if the room has been closed for a long time, for example around 5 days without any ventilation. When I first enter, I can still smell it slightly, but it’s getting better.

I’ve also been using a diffuser to help with the remaining smell. Overall, it’s nothing significant and I can tolerate it without any issue.

dammit

Thanks for the feedback @MKHmn