Which exercise equipment is suitable for strength training?

These days, parks have a variety of exercise equipment comparable to gyms. I tend not to prefer gyms because the air quality is somewhat poor, perhaps due to my bronchitis. However, park exercise equipment includes items like two-way pull-up bars, wave surfing, chair squats, rolling waist, rec press, sit-ups, and others. I am unsure whether these exercise machines are effective and which ones are most effective for strength training. I would appreciate advice from someone knowledgeable about exercise effectiveness.