Why finishing needs its own safety habits
Most wood finishing products are chemicals. Many contain solvents that are flammable and give off vapors, and some contain ingredients that can irritate skin, eyes and lungs. Water-based products are generally milder, but they are not harmless, and fine dust from sanding cured finish is a hazard of its own. This article is general information. The label, the manufacturer’s directions and the safety data sheet for your specific product always come first, and local rules apply to storage and disposal.
Read the label and safety data sheet
Before starting, read the can. Labels list hazards, protective equipment, ventilation requirements, drying and disposal instructions and what to do after skin contact or accidental exposure. A safety data sheet, available from the manufacturer, gives more detail. If the product has a warning about spontaneous combustion, take it seriously.
Ventilation
Solvent vapors are heavier or lighter than air depending on the product, and they can build up in a small shop, a basement or a garage. Good ventilation means moving fresh air through the space and exhausting vapors outdoors, not just opening one window. A fan that pulls air out of the space, with fresh air entering from another opening, works better than a fan that stirs the vapors around. Some typical considerations:
- Ventilation options for a shop range from open doors and windows to exhaust fans and dedicated systems. Cross-flow is the goal.
- Exhaust fans and anything that could spark should be designed for the vapors involved. An ordinary fan motor is a possible ignition source if flammable vapors are concentrated.
- Filters that capture dust, such as a HEPA unit, do not remove solvent vapors, so they are not a substitute for fresh air.
- Pilot lights, space heaters, open flames, sparks from tools and even static can ignite vapors. Turn off or move away possible ignition sources, and do not smoke.
- Give the finished piece and the room time to air out afterward, and keep children and pets away from drying finish.
Respirators and other protection
A dust mask is for dust. It does not protect against solvent vapors. If the label calls for respiratory protection, a respirator with cartridges rated for organic vapors is the usual type, and it must fit properly, be in good condition and be replaced on schedule. Fit matters, and facial hair can break the seal. If you are unsure which respirator suits a product, check the label or safety data sheet, or ask a supplier of safety equipment. People with heart, lung or breathing conditions should consult a medical professional before using a respirator.
For the rest of the body:
- Eye protection. Splash-resistant safety glasses or goggles protect against drips and sprays.
- Gloves. Chemical-resistant gloves, such as nitrile for many products, protect skin from solvents and stains. Check the label, as not all materials suit all solvents, and thin gloves may be penetrated by some chemicals.
- Clothing. Long sleeves and an apron reduce skin contact. Change out of soaked clothing promptly.
- Dust protection. When sanding cured finish, a dust mask or respirator rated for fine particles is appropriate, along with a vacuum to collect dust.
Wash skin with soap and water after work, and do not use solvents to clean skin unless directed by the label.
Why oily rags can catch fire
Some finishes cure by reacting with oxygen, and this reaction gives off heat. That includes drying oils like linseed and tung oil, many oil-based stains and varnishes, and some oil-containing wiping products. In a thin layer spread out in open air, the heat escapes. In a crumpled pile or a closed container, the heat can build up, and in some cases the rag can ignite without any outside flame, sometimes hours later. This has caused shop and house fires. Not every product behaves this way, and risk varies with the formula, the amount of oil, temperature and how the rags are stored. Because it is hard to judge from the outside, a cautious approach is to treat all rags from oil-based finishes as a potential hazard.
Drying and disposing of rags
Follow the directions on your product’s label first. Commonly given guidance includes:
- Spread used rags flat, in a single layer, outdoors or in a well-ventilated area away from buildings and anything flammable, until they are fully dry and stiff. Hanging them on a line with space between them is also commonly suggested.
- Some labels advise soaking rags in water and placing them in a sealed metal container with a tight lid. The container is then taken to a hazardous waste collection point.
- Check with your local waste authority, since rules for finishing rags and solvents differ by location. Many places have household hazardous waste programs.
- Never leave wadded rags in a trash can, a pile, a bag, a bin, a pocket, or on the shop floor, and never put them in a clothes dryer.
- Do not wash oily rags with household laundry unless the label says it is acceptable.
Rags that are fully dry and stiff are generally considered safer, though local rules for disposal still apply. Disposable rags and paper towels used for solvent-based products should be handled the same way.
Storing and handling products
- Keep products in their original, tightly closed containers, away from heat, sparks and direct sun.
- Store them off the floor, out of reach of children and pets, and away from living spaces if the label says so.
- Do not pour waste solvent down drains or onto the ground. Let it be taken to a hazardous waste facility.
- Use a funnel and a stable surface to avoid spills, and wipe up spills promptly, treating the cleanup materials as you would rags.
- Keep a suitable fire extinguisher nearby and know where it is. Install working smoke alarms.
Brushes, sprayers and sanding
Brushes soaked in solvent-based finish and sprayer parts being cleaned also need good airflow and careful disposal of used solvent. Sanding cured finish creates dust that can be fine and irritating; wear a respirator, keep a shop vacuum with a suitable filter handy for cleanup, and avoid creating clouds of dust near open containers. Before servicing any power tool or sprayer, unplug it or remove its battery, and follow the manual.
A short routine
Read the label, ventilate, remove ignition sources, put on the right protective gear, work in small amounts, and deal with the rags before you leave the shop. That order catches most of the common hazards, and none of it takes long. If something goes wrong, such as a swallowed product, a chemical splash, or breathing trouble, follow the first aid directions on the label and seek medical help or a poison control service without delay.