A 3.5 TOG sleeping bag can be safe when used properly. Use it in colder rooms (14-16°C). Dress your baby in suitable sleepwear underneath, avoiding overdressing. Ensure a proper fit to prevent suffocation risks. Avoid additional blankets or quilts to prevent SIDS. Regularly check your baby's temperature and adjust clothing layers for comfort and safety. Follow recommended guidelines and consult pediatric experts if needed.