Indoor fuel tank removed - How to eliminate lingering smell

Question

Background: I recently replaced my home heating system (an oil burning furnace) for a modern heat pump (air-water). There is a room in our basement (2.9m x 3.5m, or roughly 10ft x 13ft) where the 10'000 liter (~2500 gallons) tank used to be. The room was completely sealed off from the basement, save for a small window-sized opening through which you could enter to service the tank, should that be necessary.

I had a contractor cut out a door opening, and then a specialized firm came to clean the tank, cut it into smaller pieces, and recycle the steel chunks. I have now and empty room that reeks of oil, which I want to turn into a home gym. It's been some 4 weeks since we cut a door opening, and opened up the grilled vent to the outside, and although I've let enough air circulate, it still reeks as much as it did on the first day.

I assumed some oil may have leaked through the years onto the floor, which had a sort of epoxy coating, stained brown in some places. So I carefully removed it all. It took a lot of effort with a putty knife and paint scrapers. But even with a completely clean floor, it still smells. The lower half of the walls, which have the same paint/epoxy coating, have brown stains all over, which I imagine may have significant deposits of oil, perpetuating the lingering smell in the room. I read that spraying concentrated hydrogen peroxide helps eliminate all smells, so I carefully sprayed 12% hp on the walls (wearing a full body suit, goggles and a breating mask), which didn't have any significant effect overnight.

The question: is there any reasonable way (that doesn't involve overly expensive or extremely time-consuming efforts) to get rid of the smell, before I apply the decorative textured plaster on the walls? Would a controlled burn (e.g. with a small gas torch, with proper ventilation) help at all? Do you think applying plaster over the existing walls wouldn't do enough to cover the oil smell?

These pictures show the level of stains on the walls. Here you can see what I believe was pretty much the original color of the coating (first pic) vs the back wall.

Edit / Update: on Friday I primed and then used self-levelling compound (about 750lb / 350kg) to raise and level the floor, which had over 1 ¼ / 30mm height difference. The smell is completely gone. So as several of you pointed out, the oil had somehow leaked and penetrated the floor, which is now completely covered by a non porous concrete layer. Thank you all for your kind participation !!!

Answer 1

I wouldn't do a "controlled burn". If the oil penetrated deep into the wall structure. You could create more problems than you have already.

If you want to plaster the walls and protect the new plaster from the oil on the walls, for belt and braces I would use an oil based paint and cover the affected areas in the paint. If you are not sure how much of the wall is affected, paint the whole wall.

Don't immediately plaster over the dry paint though as the paint here needs additional time to set.

Once the paint has had enough additional time to set, you can jump right in and start applying the priming PVA which will help the plaster adhere firmly to the wall.

It is also advised that you select the correct plaster undercoat for painted walls, for example, see Table 1a (Plaster selection - PDF page 7) in https://www.british-gypsum.com/~/media/Files/British-Gypsum/White-Book/White-Book-C07-S02-Linings-Plaster-systems.pdf?la=en

Answer 2

This is no time for "amateur hour"

The problem with drunk-stumbling around this job is that many actions are irreversible and will block more effective efforts at cleanup. That includes:

• Application of any sort of sealer or barrier coating. Most of the time when people try this, it does little to improve the problem. However, it will "seal it" against better cleaning products, and force removal of that coating to make any more progress. That's practically a trope around here; we get lots of people who tried to seal in a smell with paint, and accomplished nothing, and now the paint is in the way of proper treatment.
• Heat, as in the odd notion of "burning out the smell", will chemically alter the surface - concrete, in particular, does not play well with heat. This too could interfere with proper removal. What's more, heating oil is a mix of several compounds, and the part that smells isn't the part that burns.

Using ordinary cleaning supplies, such as various detergents and soaps, is safe, and can be done without risk of setting yourself back. Remember, you must physically remove the offensive material. Sulfur is elemental, for instance, you can't turn it into something less smelly without a nuclear reactor or 7 years at Hogwarts. So I would be careful what you do with the rinsate (soap, water and the crud that came up). If you simply wash it out into the yard, you'll just move the smell there. I would suck it up in a Shop-Vac, and and dispose of that properly.

Honestly, rather than throwing stuff at the wall to see what sticks, it may be best to bring in professionals.

Answer 3

Since you were able to remove the sealant with a putty knife I would believe it failed and allowed some of the fuel oil to penetrate into the concrete. I use hydrogen peroxide for mold and mildew and as a sanitizer but have not heard of this use.

when cleaning concrete I use muriatic acid and water, the muriatic acid etched the surface of the concrete , if the muriatic did not take the Oder out the surface would be prepped for a 2 part epoxy paint. I have good luck sealing basement floors for moisture reasons and have used in garages this may be your only choice if the oil has soaked into the concrete. After cleaning an oil spotted floor with muriatic rinsing and allowing to dry the 2 part epoxy pains did cure and held up fine in a garage. If you want a finished wall I would use sheetrock over plaster, it can be glued directly to a dry concrete surface with construction adhesive, I usually frame it in so I can run electrical but have found many places where it was glued in place.

Answer 4

The smell comes from the volatile compounds in the oil getting into the air (the smeller) and making it to the nose (the smellee). Addressing this in some way will address the issue and these solutions fall into two main categories noted below. You might want to choose a combination from these two groups as your solution

1. Fool or protect the nose (stuff still in the air, we just don't want to be aware of them)
2. Reduce or remove the volatile compounds from the air (remove the stuff in the air)

Fooling the nose includes such things air fresheners. Protecting the nose could include things like a mask or nose plugs. Upsides include it's usually the easiest and fast solution. Downsides include it usually is short term and requires somewhat continuous effort over time.

Removing and reducing the compounds in the air can then be broken into two subgroups

1. not removing the source (stop or reduce the amount of compounds in the air)
2. removing the source (compounds no longer exist)

If the source of the compounds is not removed then the task is to reduce the amount of the compounds that are in the air or reduce the amount that get into the air. Once the compounds are in the air then can be reduced by ventilation or filtration. Lowering the amount of compounds that make it into the air from the source requires a barrier such as plastic, paint, or other coating or sealer. These options have various upsides and downsides.

Ideally, the source of the compounds is removed. Upside are that it is a permanent solution that requires no future effort. Downsides include that it is often the most difficult and expensive solution.

The answers already provided here to your question all involve a barrier of some sort and leaving (not removing) the source because it is too difficult to get at it directly.

My answer is to NOT block the compounds from entering the air but rather use time a tool. Use time instead of effort and money. When the compounds get into the air they are also being removed from the source. Literally, the source will eventually be gone. With the bonus that over this time the amount of compounds in the air will be reducing and therefore will the smell will be less and less of an issue during the process (things will always be improving). In the meantime, use a combination of ventilation and air fresheners. Protip: using a fan to blow air over the surface of the source will significantly speed up the process.