CO2 absorber:- features, types, handling, life span, color indication

CO2 absorber

CO2 absorber undergoes the mechanism of chemical reactions to absorb (nullify) carbon dioxide from the incoming air. Various types of chemical act as a CO2 absorber. However, soda-lime is mostly used in the anesthesia machine.

Some of the types of the CO2 absorber

Types of the CO2 absorber Absorptive capacity
Soda-lime 26 liters of CO2 in 100 grams of soda lime
Baralyme 26 liters/100 grams
Amsorb 10.2 liters/100 grams

Features of ideal CO2 absorbent

  • Non- toxic
  • High efficiency
  • Non- reactive to oxygen, nitrous oxide, and anesthetic drugs
  • Less resistivity
  • The granules of CO2 absorbent should be uniform in shape (for providing uniform fresh gas flow). It should consist of a mesh number of 4-8.
  • The granules should be of appropriate size. Too large granules provide insufficient surface area for absorption. Similarly, too small granules provide high resistance for the fresh gas flow.


Soda-lime is the hydroxide of calcium and sodium (or potassium). It converts carbon dioxide into calcium carbonate along with the release of water and heat.

The life span of the CO2 absorber

You should not use the absorber for more than 14 hours.

Factors affecting the life span

  • Rate of fresh gas flow
  • Amount of carbon dioxide present in the expired gas
  • The capacity of the canister
  • Handling of the canister

Color indications for CO2 absorber

Different manufacturers, manufacture CO2 absorbents by adding different kinds of dyes. These dyes react to the absorbed carbon dioxide giving out a different color. This color change is the indicator of the life expectancy of the absorbent.

Dyes Color change
Phenolphthalein Red to white
Ethyl violet White to purple
Clayton yellow Pink to cream
Titan yellow Pink to cream
Mimosa Z Red to white

If the absorber is not used for quite some time, the color might change to its initial stage. Thus this is not an effective method. Thus doctors should analyze the situation of the patient to know the condition of the absorber. An increase in FiCO2, fluctuation in the heart rate, blood pressure, etc. can be some of the symptoms.


  • Soda-lime is quite corrosive in nature. So, wear gloves and safety goggles while replacing this chemical.
  • Refill the canister properly. Else there can be leakage.
  • You can also replace it with a new one.
  • The operator should always keep an eye on the canister.
  • Set the low FGF rate as far as possible. This will keep the granules moist.
  • Turn off the oxygen flow as soon as the case is complete. Else, there can be a chance of the formation of carbon monoxide with the anesthetic agents.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button