//GenRecipe.cs
this.foodPoisonable = this.product.TryGetComp<CompFoodPoisonable>();
if (this.foodPoisonable != null)
{
    this.poisonChance = this.worker.GetStatValue(StatDefOf.FoodPoisonChance, true);
    this.room = this.worker.GetRoom();

    if (this.room != null)
        this.poisonChance = this.poisonChance * this.room.GetStat(RoomStatDefOf.FoodPoisonChanceFactor);

    if ((double) Rand.Value < (double) this.poisonChance)
        this.foodPoisonable.PoisonPercent = 1f;
}

// RoomStatWorker_FoodPoisonChanceFactor.cs
public class RoomStatWorker_FoodPoisonChanceFactor : RoomStatWorker
{
    public override float GetScore(Room room)
    {
      return Mathf.Clamp(1f / GenMath.UnboundedValueToFactor(room.GetStat(RoomStatDefOf.Cleanliness) * 0.21f), 0.7f, 1.6f);
    }
}