CONTINUED READING OF:
SIGNIFICANT CHANGES TO THE 2021 EDITION OF THE INTERNATIONAL MECHANICAL CODE
Section 403.1.3 System operation was modified to clarify that demand control ventilation schemes cannot eliminate all ventilation in a space while that space is expected to be occupied. Demand control ventilation means that the ventilation rate can be adjusted up or down as the number of occupants in a space increase or decrease. The section might be misinterpreted that the ventilation rate could reduce to zero if the number of occupants was zero. However, when the occupant load is zero, the minimum required ventilation rate is determined by the rate per square foot of floor area (Ra) in the next to last column of Table 403.3.1.1 times the net occupiable floor area of the space.
Chapter 5 – Exhaust Systems
Section 502.20 Manicure and Pedicure stations, Section 502.20.1 Operation was created to now require the continuous operation of nail salon exhaust systems during business hours. Unhealthy levels of contaminants can result in the space if the required exhaust system (source capture system) is not operating when customers are being served. The new code section will require the exhaust system to operate continuously while the space is occupied during the hours the salon is open for business.
Section 504.4.1 Termination location refers to the termination location for clothes dryer exhaust. This section was added to address the possibility of dryer exhaust air being reintroduced into a building interior. Previously, the code did not address the required separation between building openings and clothes dryer exhaust terminations. The appliance installation instructions may or may not specify such separation distances. This new section defers to the appliance installation instructions, and if the instructions are silent on the matter, a 3-foot minimum separation distance is specified. Building openings include doors, windows, ventilation and makeup air intake louvers and ventilated soffit intake openings.
Section 506.3.7 Prevention of grease accumulation in grease ducts has had a new exception added that exempts factory-built grease ducts from the duct slope prescriptions of the code, relying instead on the slope requirements stated in the product listing and manufacturer’s installation instructions. Factory-built grease ducts are tested to UL 1978 and the required minimum slope is determined by testing. Different from rectangular and square grease ducts, factory-built grease ducts are round, and the invert of the horizontal ducts is a curved channel with a much smaller surface area over which grease would flow. This allows for round ducts to have less slope than flat bottom horizontal ducts. Having less slope will ease installation for long horizontal duct runs.
Section 507.1 Commercial Kitchen Hoods General has had exception 4 which exempts smoker ovens from the requirement for a Type I hood where such ovens have an integral exhaust system and are listed for installation without a Type I hood. The new exception allows smoker ovens to be exhausted by means of an integral exhaust system that discharges to a factory-built chimney or duct system in accordance with the listing of the appliance. The appliances that fall under the new exception must be listed and labeled as suitable for venting by means other than a Type I hood.
Chapter 6 – Duct Systems
Section 602.2.1.8 Pipe and duct insulation within plenums revision addresses the practice of using pipe insulation materials to protect piping that does not meet the required fire performance requirements. The revised code states that if pipe insulation is used as the enclosing material, the entire assembly of the pipe, the insulation and any coverings and adhesives must be tested as a composite assembly.
Section 607.5.2 Fire barriers, exceptions 3, 3.1, and 3.2 describes how flexible air connectors can be installed in a duct system that is otherwise required to be constructed entirely of sheet steel. Exception 3 allows fire barrier walls to be penetrated by ducts without fire damper protection under the conditions stated in the exception.
Section 608.1 Balancing (previously Chapter 4, Section 403.3.1.5) Chapter 6 is the more logical place for balancing requirements. This revision relocates text that requires verification of the required ventilation airflow rates by means of balancing the system and adds a requirement for airflow adjustment means for air distribution and exhaust systems, in addition to the previous requirement for ventilation air systems. The new section will now require the balancing of all air conveyance systems as opposed to only ventilation air systems.
Chapter 8 – Chimneys and vents
Section 801.21 Blocked vent switch was added for an additional safety device for oil-fired appliances to be consistent with what is required for some gas-fired appliances. The required blocked vent switch detects spillage from the venting system, typically from a draft regulator installed between the appliance and the vent or chimney and shuts off the appliance. The manual reset feature prevents the appliance from operating without the intentional action by an occupant or an HVAC service person.
Chapter 9 – Specific Appliances, Fireplaces, and Solid Fuel-Burning Equipment
Section 929 Unvented Alcohol Fuel-Burning Decorative Appliances was created for a new type of decorative fuel-burning appliance which the code did not previously address. These appliances are not heaters and perform a strictly decorative function. As stated in the definition, they are stationary (not portable) and must be secured to a wall or floor. The referenced UL standard 1370 is titled: Unvented Alcohol Fuel Burning Decorative Appliances. As with all appliances regulated by the IMC, these decorative appliances must be installed in strict accordance with the manufacturer’s instructions and the conditions of the product listing.
Chapter 11 – Refrigeration
Section 1101.1.1 Refrigerants other than ammonia, this revision to the code is intended to parallel revisions to ASHRAE 15.
Section 1101.1.2 Ammonia refrigerant, this revision removes all regulations for ammonia refrigeration systems from the code and instead simply defers all regulation to the suite of IIAR standards already referenced in the code.
Section 1105.9 Machinery Room Means of Egress, egress requirements for machinery rooms from the IBC were added to the IMC to prevent such requirements from being overlooked. The IBC egress coverage is added to the IMC and is also revised relative to panic hardware. It is appropriate for refrigeration machinery rooms to have panic hardware on means of egress doors to protect occupants from the risk of a rapid release of hazardous gases. Additionally, International Institute of Ammonia Refrigeration (IIAR) 2 includes this requirement for ammonia refrigeration machinery rooms.
Sections 1107 Piping Material, 1108 Joints and Connections, 1109 Refrigerant Pipe Installation, and 1110 Refrigeration Piping System Test, previous code Section 1107 was deleted and replaced by Sections 1107, 1108, 1109, and 1110. These new code sections are more comprehensive than previous code coverage and includes expanded coverage of some topics and several new topics that were not previously covered at all.
In summary, there are over 35 changes to the International Mechanical Code in the 2021 Edition. If you have questions about how this code applies to you, reach out to us at firstname.lastname@example.org or to learn more visit iccsafe.org.
-Raoul Johnston, Senior Building and Life Safety Consultant – ICC Certified Mechanical Code Official, Certified Mechanical Code Specialist