Chemical wood impregnation in containers
Chemical wood impregnation in containers is an industrial process for protecting the wooden floorings of containers from wood‑destroying insects, fungi and mold. In practice this means that massive floor boards made of tropical hardwoods (most often Keruing, Apitong) are treated with strong pesticides or fungicides so that they last for years in the aggressive environment of maritime transport.
Why is impregnation necessary?
- The wood in containers is exposed to extreme humidity, temperature changes, salt water and biological pests.
- Without chemical treatment the floors would lose load‑bearing capacity, rot, and become hazardous for the cargo within a few months.
- The treatment primarily uses pesticide substances that penetrate deeply into the wood structure (see table below).
| Typical wood species for container floors | Impregnation method | Used substances/chemicals |
|---|---|---|
| Keruing, Apitong (tropical wood) | Pressure impregnation, surface application | Aldrin, Dieldrin, Lindan, Chlordan, CCA, PCP, creosote, ACQ, borates, copper compounds |
Note: These chemicals are extremely effective, but they also have high toxicity and long‑term persistence in the environment.
History of wood protection and impregnation
Traditional and ancient methods
- In antiquity wood was protected with natural oils (linseed, olive), tar and beeswax.
- The Romans used tar coatings on ship hulls to protect against marine pests.
- These methods were ecological but provided only a basic level of protection, suitable for less exposed applications.
Industrial Revolution: the rise of chemical preservatives
- With the advent of railways and telegraphs, the demand for long‑lasting wood surged.
- A breakthrough was the discovery of creosote (a by‑product of coal distillation), which was (and still is partially) used on railway sleepers and posts.
- In the mid‑20th century, mixtures containing chromium, copper and arsenic (CCA – chromated copper arsenate) began to be used, offering excellent protection against rot and insects.
Regulation and transition to newer technologies
- Research showed leaching of toxic components (especially arsenic) into soil, water and the food chain.
- In 2003 the USA imposed significant restrictions on CCA for residential use, followed by the EU and other countries.
- Manufacturers switched to less toxic alternatives (ACQ, CA, borates, micronised copper).
Modern chemicals and impregnation technologies
Most commonly used substances in containers
| Substance name / group | Use | Properties | Hazard level |
|---|---|---|---|
| Aldrin, Dieldrin, Lindan, Chlordan | Formerly common pesticides | Extreme toxicity, long persistence, now banned | Very high, carcinogenic |
| CCA (chromated copper arsenate) | Industrial impregnation | Excellent protection, contains arsenic and chromium | High (carcinogenic) |
| Creosote | Sleepers, posts | Excellent protection against rot | High, mutagenic |
| Pentachlorophenol (PCP) | Industrial impregnation | Effective, now heavily restricted | Very high |
| ACQ (alkaline copper quaternary) | Modern alternative | Arsenic‑free, may increase metal corrosion | Medium |
| CA (copper azole) | Modern alternative | Copper + organic compounds | Medium |
| Borates | Interiors | Non‑toxic, water‑soluble | Low |
Pressure impregnation – how it works
- Wood is placed into an autoclave (a sealed chamber).
- Air is evacuated, then the preservative solution is introduced.
- Increased pressure forces the chemicals deep into the wood pores.
- Excess solution is removed and the wood is dried.
Result: Long‑lasting protection for years, but also fixation of toxic substances deep within the structure.
Identifying treated wood in containers
Every container must have a CSC plate (Consolidated Data Plate), usually on the doors. The crucial section is “timber component treatment”, where you will find:
- Chemical type (e.g., Basileum, Talileum‑400, CCA, ACQ…)
- Date of application
- Immunity (IM) – the level of wood protection
Example entry on a CSC plate
Timber Component Treatment: IM: 25, Chemical: CCA, Date: 04/2011
Note: Replacement of the floor during the container’s life may not be reflected on the plate.
Risks to human health
Main exposure routes
- Dermal contact: Direct touch with impregnated wood.
- Inhalation: Breathing dust when cutting, sanding, or vapors at high temperatures.
- Oral intake: Especially in children, transfer from hands to mouth.
Acute and chronic risks (overview)
| Chemical | Short‑term effects | Long‑term effects |
|---|---|---|
| CCA (arsenic, chromium) | Skin and mucous membrane irritation | Increased cancer risk, skin pigment changes |
| Creosote, PCP | Irritation, headaches | Carcinogenicity, liver and nervous system damage |
| ACQ, CA | Less toxic, allergies | Low long‑term risk; possible irritation with massive exposure |
Safety recommendations when working with container floors
- Safest: Completely remove the original floor together with insulation and replace it with a guaranteed “clean” one.
- Alternative: Encapsulate the impregnated wood with several layers of solvent‑free epoxy coating or an impermeable membrane, then cover with, for example, ceramic tiles or a concrete screed.
- Always use PPE: Gloves, filter‑equipped respirator, safety glasses.
- Never burn or dispose of it casually! See further instructions.
Environmental impact and disposal
Leaching of chemicals
- Chemicals can be released into soil, water and air for decades.
- Arsenic, chromium and copper contaminate the surrounding environment, can be taken up by plants and reach groundwater.
- Burning produces extremely toxic gases and ash.
Disposal in the Czech Republic
- According to Decree No. 273/2021 Sb., chemically treated wood must be disposed of as hazardous waste.
- Transport only to specialised collection yards/facilities.
- Never throw into municipal, organic or regular wood waste.
- Cannot be chipped, composted or used as fuel.
Tip: When renovating, contact the local authority or a hazardous‑waste disposal company.
Modern alternatives for container floors
If you are building a residential or office container, consider these modern options:
| Material | Advantages | Disadvantages |
|---|---|---|
| Steel sheet | Highest durability, non‑flammable, easy maintenance | Cold surface, higher cost |
| Aluminium | Resistant, easy to clean, lightweight | Softer than steel, more expensive |
| Concrete screed | Longevity, possibility of insulation | Higher weight |
| Vinyl (coin, wood imitation) | Easy installation, various designs | Requires a vapor barrier |
| Bamboo | Rapidly renewable, ecological | Quality depends on source and processing |
Safety data sheets and documentation
- For every chemical, a safety data sheet (SDS/MSDS) must be available.
- These documents contain:
- Chemical composition.
- Hazard information and first‑aid measures.
- Handling and disposal instructions.
- Knowledge of this information is essential for operators, designers, contractors and end users.
Practical advice for owners and builders
- When purchasing a new container: Require a floor without chemical impregnation or with a modern certified treatment (ACQ, CA, borates).
- For older containers: Always check the CSC plate and, if necessary, have the wood analysed in a laboratory.
- During renovation: Prioritise removal of the original floor and ensure ecological disposal.
- If retaining the original floor: Apply an epoxy coating and an impermeable covering.
- Ensure ventilation and regularly inspect the floor and any barrier for damage.
Haiphong, Vietnam 
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