Soda lime (CAS 8006-28-8): storage and disposal
Soda lime turns up as granules in school and university stores and, more often, as carbon dioxide absorber in clinics and veterinary practices. It is classified Danger for severe skin burns and eye damage. Used granules can remain caustic, so a spent absorber is a waste item and not an empty one. Indicator colour changes can suggest exhaustion, but they are not a reliable measure of remaining absorption capacity.
- CAS number
- 8006-28-8
- Form
- Solid
- Storage class
- Alkali
- Signal word
- Danger
- Usual EWC code
- 16 05 06*
Corrosive
What to do this week
- Check the label is readable and write down the opened date if it is not already there.
- Check it is stored as alkali stock and apart from the items listed under "Do not store with".
- If you no longer need it, add it to your disposal list so it goes on the next collection.
Safe storage in a school or lab
School and college stores keep soda lime in a screw top tub, low down in the alkali store, away from acids. In a clinic or veterinary practice it is more often a sealed pack or a canister that fits an anaesthetic machine. Keep unopened packs in their original packaging until needed, and keep every tub closed, since an open tub quietly absorbs carbon dioxide from the room and loses capacity. Some older types can react with volatile anaesthetics, so confirm the type in use with the equipment supplier. Date every pack and canister on arrival.
How to tell it has deteriorated
Fresh granules look as the supplier made them, and the indicator colour is part of that. An indicator colour change may suggest that the absorber has been used or is becoming exhausted, but the absence of a change does not establish that it remains effective. On some types the colour drifts back after a rest, which can mislead, so any canister that has shown a change should be treated as used. Caked, crumbled or powdery granules and dust at the bottom of a canister are signs of age or heavy use. A cracked canister, leaking seal or crust around the lid is a leak, not ageing.
How it must be disposed of
By specialist collection only. It never goes down the drain or into general waste. It is normally packed in a corrosive alkali laboratory pack with compatible chemicals.
Spent and unused soda lime both go for specialist collection, and a used canister is described as used, not as empty. It must not go into a sink, a drain, a general waste bin or a skip, and nobody should tip out granules to lighten a canister or make it safer to carry. Collectors group it with other alkalis, away from acids. Record the form, whether tub, sealed pack or fitted canister, the size, the indicator colour if it has changed, and the setting. A veterinary or clinic holder should say if it has been in contact with anaesthetic gases.
| EWC code, laboratory chemicals | 16 05 06* |
|---|---|
| Discarded inorganic chemical, not a laboratory pack | 16 05 07* |
| Human healthcare setting | 18 01 06* |
| Veterinary setting | 18 02 05* |
| Hazardous waste | Yes |
The code depends on where the waste came from and what it is mixed with. Use the waste code finder to see why.
Do not store with
- AcidAcids and alkalis react with strong heat and spattering if they meet.
- OxidiserSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
Named chemicals to keep apart
- Acetic acidAcids and alkalis react with strong heat and spattering if they meet.
- Calcium hypochloriteSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- Hydrochloric acidAcids and alkalis react with strong heat and spattering if they meet.
- Hydrogen peroxideSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- Nitric acidAcids and alkalis react with strong heat and spattering if they meet.
- Potassium nitrateSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- Potassium permanganateSome oxidisers react strongly with alkalis, and ammonia based stock is especially at risk.
- Sulfuric acidAcids and alkalis react with strong heat and spattering if they meet.
Common quantities we collect
Usually held as: granules.
Part-used bottles and full containers are both fine. Tell us the size and how many, and an estimate is enough for a first price.
Where it is commonly held
Hazard statements
- H314 Causes severe skin burns and eye damage.
Precautionary statements
- P260 Do not breathe dust, fume, gas, mist, vapours or spray.
- P264 Wash hands and exposed skin thoroughly after handling.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
- P302+P361+P354 IF ON SKIN: Take off immediately all contaminated clothing. Immediately rinse with water for several minutes.
- P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
- P305+P354+P338 IF IN EYES: Immediately rinse with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
- P316 Get emergency medical help immediately.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P363 Wash contaminated clothing before reuse.
- P405 Store locked up.
- P501 Dispose of contents and container in accordance with local, regional, national and international regulations.
Substance as classified, dilutions may differ.
Questions
Our soda lime has changed colour. Does it need collecting?
A colour change can indicate that the absorber has been used or is becoming exhausted, but colour alone does not reliably establish its remaining capacity. Used granules can remain caustic. Treat it as waste, keep it in its canister or tub, and record it as used when booking specialist collection.
Should we worry about old soda lime and anaesthetic agents?
Some older types can react with volatile anaesthetics. Check which type your equipment uses with the supplier. If you hold old stock of unknown type, record it as unknown and include it in a collection.
How should soda lime be stored in a school?
Low down in the alkali store, in a closed, labelled tub, away from acids and out of the damp. Date it on arrival, and keep the label readable, because white granules in an unmarked tub are easily mistaken for something milder.
