Caution and Danger warning. HCl is a strong acid. Handle with care and use with care.
The reaction between sodium chlorite and a strong acid is exothermic and very violent. Because of this it is much safer to use dilute concentrations.
I strongly recommend diluting your 22.4% sodium chlorite down to a 5% concentration. Then you can use 6% HCl to activate it. The reaction is still swift, but it is much more manageable to do safely.
Caution and Danger again. Chlorine dioxide fumes are a respiratory irritant. Only mix sodium chlorite and HCl in good ventilation and be sure to protect yourself from the fumes. Chlorine dioxide is heaver than air so it will sink to the floor. If you have an animal or child, they can get a much higher exposure to the fumes than you do. Be alert and cautious.
When using 5% sodium chlorite keep in mind that you are generating about 50000 PPM in your reaction container. The fumes from this can quickly overcome you.