Sofnolime keeps you breathing underwater, but the granules are a caustic chemical. Treat a fresh drum the way you would treat lye or oven cleaner. The fine white dust can burn your eyes and irritate your lungs. Wet granules are worse. The short answer is simple. The absorbent is safe to use, and it still deserves respect every time you open the drum. This post covers how to load it, how to protect yourself, and what to do with the spent material after a dive.
Is Sofnolime Actually Dangerous to Handle?
Handled sensibly, no. Careless handling, yes. The absorbent is made from soda lime, and its active base is calcium hydroxide. In dry granule form it is a mild irritant. Add moisture, sweat, or a splash of water, and it turns strongly caustic. The real risks are dust in your eyes and lungs, and wet material sitting on bare skin.
A federal chemical hazard listing for calcium hydroxide flags irritation of the eyes, skin, and lungs, along with possible eye and skin burns. You will rarely meet enough to cause a serious burn while packing one canister. Even so, a face full of dust on a windy boat deck is easy to avoid, and it’s not pleasant.
The same care that protects you also protects the granules. Moisture is the enemy on both counts. That is why keeping an opened drum sealed and dry guards your lungs and your loop at the same time.
What Should You Wear to Pack a Scrubber?
Protect your eyes, lungs, and hands. Wear wraparound glasses or goggles, a fitted dust mask, and nitrile gloves. Pour slowly and keep the pour low inside the canister so the dust does not billow up. Work in still air, never a breeze. Do not lean over the open drum and breathe in while you scoop.
The material itself is straightforward. The maker describes diving grade Sofnolime as a product that absorbs carbon dioxide so the loop stays breathable. The dust is just fine pieces of that same caustic granule. So the whole goal is to keep it out of the air you breathe.
How you load the canister also changes how well the absorbent performs. That means how you pack fresh carbon dioxide absorbent matters as much as staying clean while you do it. A tight, even fill scrubs better and produces less loose dust.
Clean up before you dive, not after. Wipe stray granules off the rig and the deck with a damp cloth, and bag whatever you sweep up. Wash your hands before you eat or touch your face. A little dust on a bench is harmless. That same dust rubbed into a wet eye is not.
Wet Granules Become a Caustic Cocktail
When water reaches warm, working granules, it can form a caustic slurry. Divers call it a caustic cocktail. If it reaches your mouthpiece, it tastes soapy or sharp, and it can burn your mouth and throat. That’s a loop problem, not a packing problem, but it comes from the very same chemical you handled on the surface.
A flooded loop is the usual cause. So what happens when water reaches the scrubber is worth rehearsing long before it ever happens. Rinse your mouth with clean water, switch to your bailout, and end the dive. Do not try to breathe through the taste.
Prevention lives on the surface. A careful pre-breathe, a sealed loop, and a clean mushroom valve keep water where it belongs. None of that helps if you rush the checks, so build them into every setup. It’s the same discipline that keeps the dust out of your face.
How Do You Dispose of Spent Absorbent?
Bag it and bin it. Spent granules are mostly calcium carbonate, the same stuff as limestone, plus a little unreacted soda lime. In small amounts, used absorbent goes in normal household waste in most areas. Let it cool first, dampen it lightly to hold the dust down, and seal it in a bag. Check your local rules before you dump larger quantities.
Never pour used granules down a drain, and never tip them into open water. Keep spent material away from children and pets while it waits for the bin. And if a drum still holds granules but has been open too long, don’t gamble on a dive with it. Retire the drum and start fresh.
Larger amounts need more thought. A club or a charter that empties several drums a week should ask the local waste authority how to handle it, because bulk caustic waste has its own rules. Do not mix used granules with other chemicals. Label anything you store while it waits for pickup, and keep it dry and sealed.
When it is time to restock, order fresh Sofnolime 797 from Silent Diving instead of stretching a tired drum through one more dive.
Where Should You Get Fresh Absorbent?
Fresh granules and safe handling go together. Silent Diving stocks the exact 797 grade absorbent for closed-circuit rebreathers, the same consumable it supports on AP Diving Inspiration and Evolution units. If a drum has been open too long, the team would rather sell you a new one than watch you dive a weak scrubber.
Ready for a clean fill? Order fresh Sofnolime 797 from Silent Diving and store it sealed until your next dive.
If you want a second opinion on your absorbent or your unit, our rebreather service and support team can help you set a sensible replacement schedule.
Frequently Asked Questions
Is Sofnolime the same as the soda lime in a first aid kit?
No. Diving grade material is a specific granule size and purity built for rebreather scrubbers. Household or medical soda lime is not a substitute, and the wrong grade can raise your work of breathing or fail early.
Can I reuse partly used granules from a short dive?
For any serious dive, no. Once a fill has been in use, you cannot see how much capacity is left. The safe habit is to track your used time and start fresh well before the rated limit, not to guess from a short first dive.
Do I really need a mask for a single fill?
A fitted dust mask and eye protection are cheap insurance. One quiet fill in still air makes little dust. A breezy deck, a fast pour, or a clumsy scoop can put a cloud right in your face, so the habit is worth keeping every time.
How do I know a drum is too old to use?
Check the date on the drum and how it has been stored. A drum left open, damp, or through wild temperature swings is suspect. When in doubt, run a freshness check or simply replace it. The cost of a drum is trivial next to a scrubber that quits early.
What do I do if granules land on my skin?
Brush off the dry granules first, then rinse the area with plenty of clean water. If any got wet against your skin, wash longer. Watch for redness or stinging, and see a doctor if your eyes are affected or irritation does not settle.