Are The Floors of Used Shipping Containers Contaminated? Chemical Contamination in used shipping containers.

Its a very popular question and is often discussed in online forums, is it safe to work inside or live inside a shipping container? In this guide we try to offer a lot of details and dispel some of the common myths surrounding this subject.

Will a used shipping container floor have chemical contamination?

The worry is that when shipping cargo, shipping containers do move some very nasty and hazardous chemicals at times. If these were to leak out they could potentially seep into the floor, and the worry is this may make it hazardous to spend significant time inside any used shipping container. This is a very common question on shipping container home building forums and similar.

We believe this worry is highly exaggerated, and as such we would like to explain a little bit about the industry, the construction of a shipping container and how container repairs work within the industry. To try and demonstrate how small these problems are likley to be – as well as discussing possible remedies that wont’ cost the earth.

Shipping Container Design and Construction.

A Used shipping container will be sold on after approx 15 years of use ‘in service’ moving cargo around the world.

The shipping container has painted metal sides and roof, and for the purposes of this article we are assuming any potential chemical contamination could be cleaned from these surfaces with relative ease. (aside from the fact these surfaces will then usually have layers of insulation between the container wall and any living or working space)

The shipping containers also come with a floor that usually made from marine treated plywood. The treatment process does include adding chemicals that prevent bugs taking up residence in the wooden floor. This is done mainly to meet very tight Australian shipping and importing laws, but also to prevent bugs and insects making a home in a shipping container that spends its life travelling the world.

If you are totally new to shipping containers and want to know a bit more about how they are built, please feel free to check out our brief introduction to a used shipping container here:

Not all shipping containers come with a wooden floor, some designs now come with more Eco-friendly bamboo floors, which are also non-porous. (I.E. They won’t let liquids soak into the floor). These are still vary rare to see on used shipping containers but these will become more commonplace over coming years, when the current ‘in service’ fleets of shipping containers are sold off.

You can see from the introduction video above –  the vast majority of shipping containers have a marine plywood flooring throughout. This is circa 28mm thick. Underneath the floor you have a waterproofing layer (usually a bitumen based paint) and then some heavy duty steel cross-members that help support the weight of any cargo when the shipping container is being lifted.

The worry is that IF some chemicals were to leak from their containers during transit, they may seep into the floor, where they may later cause health problems for anyone living, working or spending extended periods of time within the shipping container.

How Hazardous Goods are shipped

Image showing a cut across a shipping container floor. This shows a cut going front to back – not side to side.

Also worth mentioning: The vast majority of nasty chemicals shipped around the world globally don’t move in standard shipping containers. Any chemical industry facility that uses large volumes of liquid chemicals will usually take delivery its product or ingredients in ISO container tanks which are designed for the transport of bulk liquids up to 20000 litres.

Also if you are in the UK and trying to find out how to ship your hazardous goods abroad there are 2 easy steps we suggest. 1) Get yourself a Dangerous Goods Safety Adviser, these are professionals who help make sure your hazardous goods can be shipped safely and legally. 2) The UK government has a lot of background on this, you can view this here: 

When hazardous liquids are shipped in bulk they can take 2 forms:

Limited quantities. Limited quantities of goods are allowed in transit without a declaration. For example a standard household tin of paint would not need declaring as hazardous. In many cases 1000 tins of the same paint (1000-2000 litres) would also be declared as limited quantities and may transit without a full hazardous declaration.

Standard Hazardous shipments. If you are shipping a certain volume of any hazardous substance, then over a certain volume of goods you are legally required to declare them as hazardous. These quantities are usually pretty small – and this will vary from one substance to the next.

So the the same paint from the example above sent in bulk (not in individual domestic sized tins but in one large container) would need to be shipped in UN Approved barrels or any other UN approved vessel for the goods. This same system applies for all hazardous goods. Chemicals would usually be transported in a UN approved barrel assuming there was not enough to fill a shipping container tank.

Reasonably speaking, the point we are make here is that 1) If a UN approved barrel (which will start at about 20 litres) leaks, there is no escaping this fact and it will be clear to see. Any items that is sold is a domestic quantity is probably not all that harmful, and is very unlikely to be harmful to humans in the quantities that may be likely to leak, and that also get missed in depot checks (see below).

This is a big over simplification of the entire hazardous shipping process. Any site loading large volumes of hazardous chemicals will usually be very well versed in the safe handling and loading of chemicals into shipping containers, they will check and inspect and potentially even test barrels before they are shipped, and they are fully aware if any one barrel they ship leaks, they have a very expensive repair bill from the shipping line.

Ordinarily the professionalism of anyone in the chemical industry will ensure that any chemicals are well packed. If not their customer will often not pay for the goods and they will regularly see large charges back from their shipping line for damaged shipping containers. In essence, as a chemical supplier, you wont be in business very long if you don’t ship your chemicals correctly.

The repair process for in-service shipping containers

When a container is sold off as a used container, its has often seen around 15 years of use ‘in service’, and over time shipping lines and leasing companies are learning that they can stretch this time a little long to save them money in the long run.

All shipping containers can be used to transport a range of hazardous materials. This can range from flammable liquids and solids, compressed gasses, explosives, toxic substances and even radioactive substances. The worry for potential customers looking to buy a used shipping container, is how can you be sure that previous spillages have not seeped into the floor. How can you ensure that you will be safe from harm if buying a used shipping container?

To try and help here, we are going to also look at the container cleaning and repairs structure that the industry works to.

When shipping containers are ‘in service they are looked after by the shipping line (the company that physicality owns and operated the large container vessels between ports) they may be owned by the shipping line themselves or they may be leased in from a leasing company. This ownership accounts for nearly all shipping containers that are ‘in service’ or used for shipping cargo around the world.

All used shipping containers purchased from us will have been sourced from one of these shipping line or leasing companies, we will always make it clear to you if a container we are offering has not come from our usual industry sources. This gives our used range the best possible lifespan and ensures a good consistent quality of storage container when we sell it on.

When these ‘in service’ containers have done their final shipment, they are returned empty to a container yard. This yard checks over each and every container that comes into their yard, and they will give their customer (the container owner or the person looking after it) a repair estimate. The yard is there to repair anything that prevents the container being re-used for shipping, and one major potential cost is new flooring.

Commonly, any oil seepage (that’s one issue we see regularly) gets into the floor, and once its in the floor there is no easy way to clean it out.  The only way to bring the container back to an ‘in service’ standard is to either section or replace the floor panel (for very minor spillages it may be possible to grind back a bit of the floor panel, but more than a mm or two and the industry requires a replacement)  A very small spill and they may cut the section of floor out and add in a new section or add a very small plate over the hole. If this isn’t practicable, then a whole new floor panel will be required. The depot is incentivised to quote for this, as they make their money from repairing shipping containers.

So in the example of a chemical spillage that seeped into the floor, any sizable spillage would have been picked up, the shipping line would have been billed for the replacement floor, and the shipping line more then likely passed this charge onto their customer (the person who caused the damage, or responsible for the damage). Its is reasonable to say that such a spillage may get missed if its very small, but any reasonable sized spillage would get picked up and billed forward.

If the shipping lines did not do this as a matter of course, the next customer loading the shipping container would be very likely to reject it. If the shipping line did this regularly the next customer would find a new shipping line to deal with. As a whole the industry cannot operate in this way and they need to provide a consistent, reliable level of service here, or face loosing business to their competitors.

What happens when you buy a shipping container from budget shipping containers

When we buy in a batch of shipping containers from a shipping line or leasing company, they are commonly already in the depot. We either buy them in a cargo-worthy condition (which means they have already been checked and repaired to export standards) or we buy them in ‘as is’ condition, and then do these same checks ourselves.

Its very common if we move them into a different yard, that a container may get checked twice by 2 separate yards, but it will always be checked at least once in this process.

We then ask the depot to repair any containers to a seaworthy standard, or an equivalent if being used for storage.

In any case as above – the depot will quote for the replacement of any contaminated or stained floor panel if there is any liquid spillage other than water that has soaked into into the plywood, and we would never knowingly sell a shipping container with any form of contamination.

In the very worst case, if you purchased a shipping container from us that arrived with clear chemical contamination, then you would be within your right to refuse the delivery and as per our guarantee and returns policy. Its up to us to repair the container or sort the contamination out for you, or if we can’t we then have to replace the shipping container. Not all container traders offer this level of guarantee to their customers.
It is worth adding that used containers will commonly have heavily worn and scarred floors from years of use. Ingrained dirt is very common to see and we would not accept a return simply because a container floor looked a little worn, dirty or well used.

After delivery

Shipping Container Floor

Once the shipping container has been delivered, you will often ordinarily start working on this. If you are reading this article you are likely planning a container home, office, workshop or other similar conversion that would involve someone spending a lot of time inside the shipping container. In these examples its very natural to have concerns about potential contamination issues.

What you do with the container floor between delivery and using the container will also have a big impact on the risk of any contamination.

Very few customers leave a bare floor. Many want to either remove the floor completely, or cover it. With relation to continuation there are 5 obvious routes here.

  1. If you leave the floor ‘as is’ and if you are unhappy with the way the industry may have looked after the container (from the info above) then there is a small chance that small areas of floor panel may have had a chemical spillage at some point in the past.
  2. If you remove the floor panels, you have nothing to worry about. Make sure that all the metal surfaces are cleaned before your convert the container and you will be good to go!
  3. If you wish to sand down the top layer of the plywood down, but to keep the original container floor in place, this is also very do-able, and evidence of any chemical seeping into the plywood floor should be evident once you sand the top (dirty) layer from the plywood.
  4. If you wish to overlay a flooring material over the container floor, this is also very achievable. If you ensure the container floor is sealed then we can’t see any way any potential chemicals could potentially get back into your living / working space. We would suggest a vinyl or lino flooring that is sealed around the edges of the original container floor, but there will be many other options that give you a good seal between the original container floor and your new internal flooring material.
  5. You can also seal the floor various ways. Varnishes, waxes and paints are obvious options used on other wooden floors.

How bad is this chemical ?

As mentioned, we are shipping container experts and not chemical experts. If anyone with a strong background here would like to offer any additional comment or info we will be happy to publish your comments here with a credit and link.

However, for a chemical to seep into your container and then come back out of the floor at a much later date and cause health issues, we feel this will have to be limited to a very small number of potential chemicals.

We already offer formaldehyde free storage containers for specific uses, and we have done our reading here! we are aware that formaldehyde will seep out of the container over the first couple of weeks and then levels will be negligible.

For a chemical to spill into the floor and then cause you health issues later on it will need to have all of the following traits:

  • It would have to be very dangerous at very small quantities, or it would somehow have to be able to seep into the floor without leaving a mark or stain
  • It would be odorless and colorless, otherwise you would be able to spot its presence or smell it.
  • It would need to still be dangerous having already seeped into the floor, and being able to seep out again naturally at a later date
  • It would have to be toxic in extremely small quantities (as the amount of chemical that would come back out of the wood again once it had been impregnated would be extremely small)

Now to our knowledge, if any such chemical did exist, there would probably be extra special stringent conditions on its movement and transport, as it would have the capacity to infect a lot more than shipping container floors in the event of a leak or similar issue. Again we are happy to invite chemical industry and chemistry experts to advise here, but the shipping industry is very well versed in ensuring hazardous shipments are handled safely.

Overall, whist we feel that concerns over chemical contamination in shipping containers is only natural if you are goign to spend significant amount of time inside a converted shipping container.  We feel that when buying from a reputable firm, and if sealing the floor before re-use there shouldn’t be any worry for an end user when buying used shipping contianers for their own conversion work. Giving the metalwork a good clean, and sealing the floor should provide a physical barrier between any potential chemical spillage and your living or working space.

Whilst we cannot guarantee that every shipping container is chemical free, the chances of dangerous chemicals being present that could then seep out into your container are extremely small at best, and this is before any remedial actions you can take to seal or remove the plywood flooring in the shipping container.

One trip (new) Shipping Containers vs Used shipping containers.

The choice to build with new or used shipping containers is a wide one and will be the subject of another post very shortly.

However in specific relation to the potential contamination in container floors

Used shipping containers will be approx 15 years old and have been used to ship goods around the work for this circa 15 year lifespan.

a One trip (new) container is built in china and has only done one trip with cargo in from factory to your country. *

A one trip container will have done significantly fewer shipments (one instead of approx 500), so your container is approx 500x less likley to have ever shipped chemical inside. Shipping lines will often use regular customers / established regular shipments with their new containers as they know there is less likelihood of damage and wear, but all of this only improves your chances of no issues, it wont’ give you a cast iron guarantee.  Few traders will be able to guarantee that a one trip shipping container has never had hazardous chemical inside.

* we would like to stress that any one trip container purchased from budget shipping containers has only done one trip. We are aware some containers sold as one trip or new containers may have done 2 trips, or may have been out on a hire for storage use once its done its first trip and before being sold on. This would never knowingly be the case with us but we can’t guarantee what others do here.

Radiation in Shipping Containers

We did briefly mention this earlier

Whilst shipping containers are used to move radioactive goods, you should not worry about potential radioactive contamination.

The nuclear industry has their own fleet of specialised shipping containers for moving highly radioactive materials. These are thoroughly tested at all times to ensure there is not dangerous levels of contamination beyond the single container itself, and these containers would never be sold off to any third party without numerous contamination checks being done, and as they used very special half height containers which are heavily lined to prevent radiation getting out of the container, they would not commonly be any use to an end customer for a storage container.

If a container is ever carrying very radioactive substances, the load is carefully tested before departure to ensure it cannot contaminate goods stowed nearby. (The containers are usually concrete lined to prevent harmful levels of radiation escaping)

Low level radioactive shipments are also very tightly controlled. As soon as a shipment is declared and labelled as hazardous nuclear materials, a unique set of shipping and handling standards are used, much in the same way that explosives have their own protocols for handling and movement. You cannot ship any radioactive goods in or out of a UK port without the port authority and customs knowing about it. This makes mis-declarations (ie someone telling customs that their dangerous cargo is something completely different to save costs / time and perhaps taxes) a near impossibility for any radioactive substance.


We are shipping container experts and not chemical experts.

Whilst we have done our best to give you a clear, factual write up here – that hopefully helps you make an informed decision on weather this product is right for you or not. We would like to highlight that we provide no guarantee or indemnities against all potential issues.

If you have any specific relevant expert knowledge on the chemical side of things and would like to contribute please let us know. We will need to check any content, but we will include a credit and a permanent link in this article for any contribution.

Do you need a shipping container for conversion use (or even just for storage?) offer the UK’s largest online range of shipping containers for sale with a nationwide network of storage and conversion yards and crane equipped delivery vehicles.

If you need a shipping container feel free to browse our online range of shipping containers for sale, which also includes our ranges of flat pack sheds, container canopies and more. You can also call us on freephone 0808 1234 215 any time 9am – 7pm weekdays and our team will be happy to discuss your requirements. Alternatively, you can use our online shipping container quote form or request a telephone callback. In both cases we aim to get back to you within 1-2 working hours (may take longer for more detailed quotes).

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