Mazda MX-5 Miata Sport 2007 Manual page 1427

Fig. 7: Identifying High & Low-Pressure Side Readings Of Manifold Gauge
Courtesy of MAZDA MOTORS CORP.
WARNING:
18. Open the low-pressure side valve of the manifold gauge and charge with refrigerant until the weight of
refrigerant tank has decreased 200 g {7.06 oz} from the amount in Step 13.
2007 Mazda MX-5 Miata Sport
2007 HVAC Refrigerant System - MX-5 Miata
If charging the system with refrigerant by service cans or

refrigerant tank, running the engine with the high-pressure side
valve open is dangerous. Pressure within the service cans or
refrigerant tank will increase and they could explode,
scattering metal fragments and liquid refrigerant that can
seriously injure you. Therefore, do not open the high-pressure
side valve while the engine is running.