Sodium hydroxide (caustic soda) COSHH assessment guide

Caustic soda is used for drain clearing, paint stripping, soap making and cleaning. As a solid it causes severe skin burns and eye damage, and it can corrode metals.

Taken from the Sodium hydroxide pellets (100%) safety data sheet from Fisher Scientific UK, revision 20 October 2023. Open the data sheet. Formulas differ between products, so check against the sheet for the product you actually buy. This is a laboratory-grade sheet. Trade products sold under the same name can have a different strength and different hazards. It covers the 100% solid. Solutions are classified by strength. Its advice to work under a fume hood is written for laboratories.

Hazards on the data sheet

Signal word: Danger.

H290 May be corrosive to metals
H314 Causes severe skin burns and eye damage

Precautions

P280 Wear protective gloves/protective clothing/eye protection/face protection
P301 + P330 + P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting
P303 + P361 + P353 IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water or shower
P305 + P351 + P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing
P310 Immediately call a POISON CENTER or doctor/physician

Workplace exposure limit

Short-term (15-minute): 2 mg/m³. From EH40/2005 Table 1. It sets a short-term limit only, and no long-term limit.

PPE

Eyes	Goggles (European standard - EN 166).
Hands	Protective gloves. Neoprene: > 480 minutes, 0.45 mm. Butyl rubber: > 480 minutes, 0.35 mm. Viton (R): > 480 minutes, 0.30 mm. EN 374, Level 6.
Breathing	Certified respirators when facing concentrations above the exposure limit. Large scale/emergency: Particulates filter conforming to EN 143. Small scale/laboratory: EN 149:2001 approved respirator; half mask EN405, or EN140 plus filter EN 141.
Skin	Long sleeved clothing.

First aid

Eyes	Rinse immediately with plenty of water, also under the eyelids, for at least 15 minutes. Immediate medical attention is required. Keep eye wide open while rinsing.
Skin	Wash off immediately with soap and plenty of water while removing all contaminated clothes and shoes. Call a physician immediately.
Breathed in	Remove to fresh air. If breathing is difficult, give oxygen. Do not use mouth-to-mouth method if victim ingested or inhaled the substance; use a pocket mask with a one-way valve or other proper respiratory medical device. Call a physician or poison control center immediately.
Swallowed	Do NOT induce vomiting. Immediate medical attention is required. Never give anything by mouth to an unconscious person. Drink plenty of water.

Storage, spills and what to keep it away from

Storage	Keep containers tightly closed in a dry, cool and well-ventilated place. Corrosives area.
Spills	Evacuate personnel to safe areas. Avoid contact with skin, eyes or clothing. Avoid dust formation. Sweep up and shovel into suitable containers for disposal. Do not flush into surface water or sanitary sewer system.
Keep away from	Strong oxidizing agents. Acids. Metals. Water. Alcohols.

What your assessment still has to cover

Dust and dissolving are the stages to look at. Record who weighs or pours the solid, how it is mixed, and where eye-wash and running water are. This sheet lists water among the materials to avoid, so write down exactly how it is dissolved.

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