How to Clean a Shipping Container – and When It Matters

How Does Dirt Get Into a Shipping Container?

Standard palletized goods like shrink-wrapped boxes cause little contamination inside the container. However, in addition to so-called general cargo, shipping containers are often used to transport goods that are far less sterile. Food products such as grain, coffee, and cocoa are frequently shipped in bulk bags. Construction materials like gravel and sand are loaded as loose bulk goods, which naturally creates a lot of dust. Fresh produce is transported over long distances in refrigerated containers and can sometimes emit strong odors. Accidents can also happen: cargo may be improperly packed, liquids may leak during transport, or animals may sneak in as stowaways and leave droppings on the container floor.

Can Shipping Containers Be Contaminated with Hazardous Substances?

Here’s some reassurance for buyers of second-hand containers: If you purchase an old shipping container, you generally don’t need to worry about health risks due to contamination. According to international regulations, hazardous materials are not permitted for transport in standard ISO containers. This ban includes, for example:

• Corrosive substances such as sulfuric acid or alkaline battery electrolytes
• Toxic substances like pesticides
• Flammable liquids such as motor oil, gasoline, or turpentine
• Radioactive materials

These types of goods are also shipped across the globe, but only in specially approved containers designed for that purpose.

What Does Cleanliness Mean in a Shipping Container?

Major shipping lines like Maersk have strict guidelines for cleaning a container before handing it over to the next carrier.

According to these standards, a clean container must be free from:

• Labels and stickers
• Sand, soil, dirt, mud, cargo residues, and waste
• Insects, fungi, and animal droppings
• Cargo securing elements such as ropes, chains, cables, or tension straps
• Adhesive tape and packaging film
• Glue residue or other materials sticking to the floor, walls, or ceiling
• Nails, bolts, or other fasteners installed above floor level
• Unpleasant odors that could contaminate the next cargo
• Damp spots, e.g., from hydraulic fluid
• Loose sealing compound

Refrigerated containers in particular must show no traces of organic material or odors after use.

How Do I Clean a Container?

If you’re repurposing a used shipping container as a tiny home or storage space, you’ll want to remove all traces of its previous use. The best way to do this is to follow a step-by-step process:

1. Sweeping: Use a stiff outdoor broom to sweep out coarse sand and dust from the container floor, working from the back wall toward the doors. Ideally, wear a dust mask to avoid inhaling particles. Sweeping alone often isn’t enough to fully remove dust, so many start directly with step 2.
2. Vacuuming: Having access to an industrial vacuum cleaner is a big advantage. It removes loose dirt from the floor as well as dust clinging to the walls and ceiling.
3. Pressure Washing: A good pressure washer can be rented from a hardware store or borrowed from a neighbor. All you need nearby is access to electricity and water to get the container sparkling clean. Be cautious—pressure washing isn’t risk-free. Protective goggles are essential, as sharp debris or water spray may bounce back. Start by pressure washing the interior from back to front and top to bottom. The water jet also reaches into corners and cracks, making signs of wear more visible. On the outside, pressure washing removes flaking paint and reveals any rust damage. Repairs should be done once the container has fully dried.
4. Rust Treatment: After cleaning, carefully inspect both the interior and exterior for rust damage. You can use commercial rust removers or go the DIY route with a wire brush and vinegar. First, scrub off loose rust, then apply a 50/50 mix of vinegar and oil generously to the rusty areas. Let it sit for a few hours, then rub it off firmly to remove any remaining rust particles.
   Tip: Rust removal is much more efficient with a sandblaster, though these aren’t always available to private users. An alternative is wet sandblasting, where a pressure washer draws in quartz sand through an extra hose and adds it to the water jet.
5. Patching Rust Holes: Small rust holes, about the size of a 5-cent coin, can be patched without welding. Use metal filler or fiberglass-based body filler. Apply the mixture, reinforce with mesh if needed, and sand it down once it’s hardened. For larger holes, welding in a metal patch is the only option. Alternatively, the hole could be repurposed as a space for a window to bring light into your container home.
6. Painting: Once the container is dry and all rust damage is treated, a fresh coat of paint completes the renovation. One-coat paints are especially practical since they eliminate the need for a primer.