No nuisance tripping on motor starts; that's what C or D curves handle.
The 40 A rating holds at 35 °C ambient; it derates to 38.4 A at 40 °C, 37.6 A at 45 °C, 36.76 A at 50 °C, 35.92 A at 55 °C, and 35.04 A at 60 °C. That thermal curve is what the panel builder needs for fill-factor calculations inside a sealed enclosure — don't load the breaker to 40 A if the cabinet runs at 50 °C.
Mounting position is any orientation, so it fits tight sub-distribution boards where vertical or horizontal rail layouts are used. Neutral conductor is switched (3P+N), which means the neutral pole opens and closes with the phases — required in some industrial specs to isolate the circuit completely.
Rated to IEC / EN 60898-1 and IEC / EN 60947-2, plus UL1077. That dual rating covers both residential-style MCB applications (EN 60898) and industrial circuit-breaker duty (IEC 60947-2) — the same part works in a UL 508A panel and a European-style distribution board. The sealable option (padlockable toggle) lets maintenance lock the breaker in the off position for LOTO procedures.