J4 J4 California Residential Mechanical Inspector Certification Exam

J4 J4 California Residential Mechanical Inspector California inspectors routinely miss questions about damper operation in forced-air systems and miscalculate duct sizing requirements, even when they’ve conducted hundreds of field inspections. The J4 exam tests nuanced code provisions that diverge from common practice, particularly around refrigerant charge verification and combustion air pathways. Field experience alone won’t catch these gaps—deliberate study of the California Mechanical Code’s specific language is essential.