At what density does helium burning start in a star?

From this webpage, I have a few statistics regarding required density and temperature to burn a specific element.

Burning phase; Required temperature; Required mean density; Duration

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Hydrogen burning: $4 times 10^7 text{ degrees K; } 5 text{ gm per cubic cm; } 7,000,000 text{ years}$

Helium burning: $2 times 10^8 text{ degrees K; } 700 text{ gm per cubic cm; } 700,000 text{ years} $

Carbon burning: $1 times 10^8 text{ degrees K; } 200,000 text{ gm per cubic cm; } 600 text{ years} $

Neon burning: $1.2 times 10^9 text{ degrees K; } 4,000,000 text{ gm per cubic cm; } 1 text{ year} $

Oxygen burning: $5 times 10^9 text{ degrees K; } 10,000,000 text{ gm per cubic cm; } 6 text{ months} $

Silicon burning: $2.7 times 10^9 text{ degrees K; } 30,000,000 text{ gm per cubic cm; } 1 text{ day} $

This is data for a star of 25 solar masses.