This former Blogger draft was fully rewritten, fact-checked and updated in July 2026.
RGBM stands for Reduced Gradient Bubble Model. The name is often used as though every RGBM computer runs the same transparent calculation, but implementations differ and some are proprietary or manufacturer-modified.
This article focuses on the Suunto RGBM documentation because that is a clear practical example of how a manufacturer describes its system.
Dissolved gas and free gas
Traditional compartment models estimate inert gas uptake and elimination in theoretical tissues. Suunto describes its RGBM implementation as considering both dissolved gas and free-gas or microbubble behaviour, then reducing permitted gradients when certain dive patterns are associated with greater decompression stress.
Which patterns can affect the guidance
- Repetitive and multiday diving.
- A dive deeper than the previous dive.
- Rapid ascent or omitted safety guidance.
- Short surface intervals and residual exposure.
- User-selected personal or altitude settings.
How the computer may respond
Depending on the implementation and profile, the computer may shorten no-stop time, lengthen decompression, add mandatory safety-stop requirements or recommend a longer surface interval. This is not a simple “group system,” and the exact behaviour depends on the product generation and settings.
What “dive history” really means
The computer uses the depth-time and gas profiles it has recorded during the repetitive series. It does not know the diver’s medical history, hydration, fatigue, thermal stress or actual bubble load. If the computer did not record a previous dive, it cannot reconstruct that exposure reliably.
The model’s limit
RGBM is a mathematical risk-management tool, not a sensor inside the body. Following it does not guarantee freedom from decompression sickness. Use the same computer throughout the series, understand its personal settings and avoid treating every displayed minute as a target.
Continue the model series
The companion articles Bühlmann ZHL-16C in Dive Computers and Bühlmann vs RGBM explain another common model and the practical differences between the two approaches.
