Even methane (natural gas) is lighter than air, but not by much. Carbon dioxide, which is contained in the air we breathe out and is also easily and safely manufactured by mixing bicarbonate of soda and vinegar, is heavier than air. It tends to sink to the floor and accumulate. So it's a good job that houses aren't air tight.
Cuddling, holding, and sexual play releases chemicals, like oxytocin, in the brain that create a sense of well-being and happiness, says Dr. Renee Horowitz, an ob-gyn who recently opened the Center for Sexual Wellness in Farmington Hills, Michigan.
In response to seeing the bear, a part of the brain called the hypothalamic-pituitary-adrenal (HPA) system is activated. Release of Steroid Hormones and the Stress Hormone Cortisol. The HPA systems trigger the production and release of steroid hormones (glucocorticoids), including the primary stress hormone cortisol.