The coronavirus disease 2019 pandemic has led to the manufacturing of novel devices to protect clinicians from the risk of transmission, including the aerosol box for use during tracheal intubation. We evaluated the impact of two aerosol boxes (an early-generation box and a latest-generation box) on intubations in patients with severe coronavirus disease 2019 with an in-situ simulation crossover study. The simulated process complied with the Safe Airway Society coronavirus disease 2019 airway management guidelines. The primary outcome was intubation time; secondary outcomes included first-pass success and breaches to personal protective equipment. All intubations were performed by specialist (consultant) anaesthetists and video recorded. Twelve anaesthetists performed 36 intubations. Intubation time with no aerosol box was significantly shorter than with the early-generation box (median (IQR [range]) 42.9 (32.9-46.9 [30.9-57.6])s vs. 82.1 (45.1-98.3 [30.8-180.0])s p = 0.002) and the latest-generation box (52.4 (43.1-70.3 [35.7-169.2])s, p = 0.008). No intubations without a box took more than 1 min, whereas 14 (58%) intubations with a box took over 1 min and 4 (17%) took over 2 min (including one failure). Without an aerosol box, all anaesthetists obtained first-pass success. With the early-generation and latest-generation boxes, 9 (75%) and 10 (83%) participants obtained first-pass success, respectively. One breach of personal protective equipment occurred using the early-generation box and seven breaches occurred using the latest-generation box. Aerosol boxes may increase intubation times and therefore expose patients to the risk of hypoxia. They may cause damage to conventional personal protective equipment and therefore place clinicians at risk of infection. Further research is required before these devices can be considered safe for clinical use.