Hazardous substances: why it matters
Construction uses chemicals, dusts and materials that can harm you long before any obvious injury: cement burns the skin, solvents affect the brain, and asbestos kills decades later. Controlling them is a legal duty and a major test topic.
The key law is the Control of Substances Hazardous to Health Regulations 2002 (COSHH). Before work starts, hazardous substances must be assessed, prevented or controlled at source, with PPE only as a back-up.
Hazardous substances revision notes
Most hazardous substances questions come back to the COSHH method: assess first, control the substance at source, and treat PPE as the back-up rather than the answer. Learn that order and the routes of entry from the notes below and you can reason out the rest.
COSHH in four steps
Assess the substances and who is exposed, prevent exposure where you can, control what is left at source, and use RPE or PPE only for the residual risk. Review the assessment when things change.
Routes of entry
Hazardous substances get in by inhalation (breathing), ingestion (hand to mouth), absorption (through the skin) and injection (through a cut). Good hygiene and the right PPE block these routes.
Read the label and SDS
Suppliers provide a safety data sheet and warning pictograms (the orange and white CLP symbols). They tell you the hazards, controls, first aid and safe storage. Read them before you use the product.
Asbestos is special
Asbestos is the biggest single cause of work-related deaths. It is covered by its own regulations. If you find or suspect asbestos, stop work, do not disturb it, and report it. Higher-risk work must be done by a licensed contractor.
Cement and wet concrete
Wet cement is highly alkaline and causes serious chemical burns and dermatitis. Keep it off the skin, wash it off promptly, and wear suitable gloves and protection.
Storage and spills
Store substances as the data sheet says, keep them secure and labelled, and have spill kits and bunding so nothing reaches drains or the ground.
Hear a question in Polish
COSHH questions often hang on a single detail, a route of entry into the body or what a safety data sheet tells you to do. Press Play in Polish below to hear a real question read aloud while you follow the English.
What feature distinguishes a substance as 'hazardous' under COSHH?
Color
Texture
Potential to cause harm to health
Odor
Every wrong answer can also come with an AI explanation that points to the specific rule behind the correct answer, so you learn from each mistake instead of just memorising. Native Polish audio and AI explanations are two things you will not find on other CSCS practice sites.
Hazardous substances quiz, five questions
Five hazardous substances questions in the real CITB format. Watch for the ones on routes of entry and the order of control, where people slip up. Answer each one and it is marked straight away, with the reason it is right.
0 of 5 answered
Score: 0 / 5
Q1. What should you do first if you come into contact with a hazardous substance?
Reveal explanation
Correct answer: B. Wash the affected area thoroughly
Immediately washing the affected area helps to remove the substance and minimize exposure.
Q2. What is the primary purpose of COSHH regulations?
Reveal explanation
Correct answer: C. To control hazardous substances to prevent harm to health
COSHH regulations are designed to control substances that are hazardous to health and prevent harm.
Q3. Which of the following is a potential effect of exposure to hazardous substances?
Reveal explanation
Correct answer: B. Skin irritation
Exposure to hazardous substances can lead to skin irritation among other health issues.
Q4. Under COSHH, who is responsible for assessing the risk of hazardous substances?
Reveal explanation
Correct answer: C. Employers
Employers are responsible for assessing and mitigating the risks involved with hazardous substances.
Q5. Which symbol is used to indicate a toxic chemical under COSHH?
Reveal explanation
Correct answer: B. A skull and crossbones
A skull and crossbones symbol indicates a toxic chemical, suggesting it can cause severe health effects.
Answer all five to see how you did on hazardous substances
The real CITB test is 50 questions in 45 minutes, with a 45 out of 50 pass mark. Our free mock test uses the same format and needs no account.
Common mistakes
These substance-handling beliefs cause harm that shows up days or decades later, not just a wrong mark. Unlearn them before the test and before your next task with chemicals or dust.
Mistake 1: “COSHH does not cover dust.”
Correct: COSHH covers many dusts, fumes, gases and biological agents, not just liquids in containers. Silica and wood dust are classic COSHH hazards that must be assessed and controlled.
Mistake 2: “Any gloves protect against any chemical.”
Correct: Chemicals can pass straight through the wrong glove material. Gloves must be chosen for the specific substance using the data sheet, and changed before they are saturated.
Mistake 3: “Asbestos is only in old factories.”
Correct: Asbestos can be in any building constructed or refurbished before the year 2000, including houses, schools and offices. Always check the asbestos register before disturbing materials.
Related CSCS topics
Hazardous substances overlap with the other health hazards on site. These related areas round out the picture: