The expanded line of M-Series direct gas-fired makeup air heaters and accessories includes a new, vertical mounting option for both indoor and outdoor applications. Also available are rooftop, through-the-wall, under-the-roof, and horizontal pad mount options. The company says its makeup air heaters are used to heat and provide fresh, tempered make-up air to replace building exhaust from both new and existing facilities, including warehouses, distribution centers, factories, painting areas, and other commercial/industrial facilities.