Md. Code Regs. 09.12.01.03 – Air and Ventilation.

A. A boiler room shall have a permanent source of outside air to:
1. (1) Permit satisfactory combustion of fuel; and
2. (2) Provide proper ventilation of the boiler under normal operating conditions.

B. Louvered area.

(1) The total requirements of all burners for all fired pressure vessels in a boiler room shall be used to determine the louver sizes, whether the pressure vessels are fired by coal, oil, or gas.
(2) The minimum net free louvered area shall be at least 1 square foot.
(3) The minimum dimension of air openings may not be less than 3 inches.
(4) Ducts, when used, shall be of the same cross-sectional area as the free area of the openings to which they connect.
(5) The following configurations shall be used:
1. (a) Two permanent openings:
  1. (i) One opening shall start within 12 inches of the ceiling, and one opening shall start within 12 inches of the floor;
  2. (ii) The openings shall connect directly, or by ducts, with the outdoors or with crawl or attic spaces that freely connect with the outdoors;
  3. (iii) Where directly connecting with the outdoors or where connecting to the outdoors through vertical ducts, each opening shall have a minimum free area of 1 square inch per 4,000 Btu per hour of total input rating, or total relieving capacity, of all fired pressure vessels, whichever is greater; and
  4. (iv) Where connecting to the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 square inch per 2,000 Btu per hour of total input rating, or total relieving capacity, of all fired pressure vessels, whichever is greater; or
2. (b) One permanent opening:
  1. (i) The opening shall start within 12 inches of the ceiling;
  2. (ii) The opening shall directly connect with the outdoors, or shall connect through a vertical or horizontal duct to the outdoors or with crawl or attic spaces that freely connect to the outdoors; and
  3. (iii) The opening shall have a free open area of 1 square inch per 3,000 Btu per hour of total input rating, or total relieving capacity, of all fired pressure vessels, whichever is greater.

(6) The following table shall be used to determine the net louvered area in square feet:

Input Btu per Hour	Required Air CFM	Vertical Ducts Minimum Net Louvered Area Sq. Ft. per Opening	Horizontal Ducts Minimum Net Louvered Area Sq. Ft. per Opening	Single Opening
100,000	50	0.50	0.50	1.00
200,000	100	0.50	0.69	1.00
300,000	150	0.50	1.04	1.00
400,000	200	0.69	1.39	1.00
500,000	250	0.87	1.74	1.16
750,000	375	1.30	2.60	1.74
1,000,000	500	1.74	3.47	2.31
1,250,000	625	2.17	4.34	2.89
1,500,000	750	2.60	5.21	3.47
1,750,000	875	3.04	6.08	4.05
2,000,000	1000	3.47	6.94	4.63
2,500,000	1250	4.34	8.68	5.79
3,000,000	1500	5.21	10.42	6.94
3,500,000	1750	6.08	12.15	8.10
4,000,000	2000	6.94	13.89	9.26
4,500,000	2250	7.81	15.63	10.42
5,000,000	2500	8.68	17.36	11.57
6,000,000	3000	10.42	20.83	13.89
7,000,000	3500	12.15	24.31	16.20
8,000,000	4000	13.89	27.78	18.52
9,000,000	4500	15.63	31.25	20.83
10,000,000	5000	17.36	34.72	23.15
11,000,000	5500	19.10	38.19	25.46
12,000,000	6000	20.83	41.67	27.78
12,500,000	6250	21.70	43.40	28.94

C. Mechanical Combustion and Ventilation.
1. (1) Mechanical ventilation may be used to supply combustion air or ventilation air, or both, to a boiler room.
2. (2) When mechanical ventilation is used:
  1. (a) The firing device shall be interlocked with the fan so that the firing device cannot operate without proven airflow;
  2. (b) The velocity of the air passing through the louvers cannot exceed 500 feet per minute; and
  3. (c) The total air delivered shall be equal to or exceed 0.5 CFM per 1,000 Btu per hour of total input rating or total required relieving capacity, whichever is greater.
D. Water Heater Combustion Air Ventilation Requirements.
1. (1) Hot water heaters in excess of 200,000 Btu per hour up to but not including 1,000,000 Btu per hour, that are located in their own equipment room, shall have at least:
  1. (a) 1 permanent source of outside air; and
  2. (b) 1 square foot of total net free louvered air space.
2. (2) Hot water heaters of 1,000,000 Btu per hour or greater shall follow manufacturer's requirements.
3. (3) Hot water heaters with inputs and required relieving capacities less than 200,000 Btu per hour are not covered by this regulation.

Authority: Public Safety Article, Title 12, Annotated Code of Maryland
Ch. 351, Acts of 2004

Effective date: October 15, 1975 (2:23 Md. R. 1414)

Regulation .02CC amended and .02DD repealed effective June 1, 1982 (9:8 Md. R. 821)

Regulation .02PP amended effective November 4, 1985 (12:22 Md. R. 2103)

Regulations .07—.08 adopted effective November 4, 1985 (12:22 Md. R. 2103)

Regulations .01—.08 repealed and new Regulations .01—.32 adopted effective June 1, 1989 (16:10 Md. R. 1106)

Regulation .01B amended effective September 1, 1989 (16:16 Md. R. 1749); April 16, 1990 (17:7 Md. R. 848); October 7, 1996 (23:20 Md. R. 1422); June 30, 1997 (24:13 Md. R. 930)

Regulation .01B amended as an emergency provision effective July 14, 1999 (26:16 Md. R. 1237); amended permanently effective October 4, 1999 (26:20 Md. R. 1545)

Regulation .01B amended effective July 10, 2000 (27:13 Md. R. 1211)

Regulation .01-1 amended effective January 31, 1994 (21:2 Md. R. 98); July 18, 1994 (12:14 Md. R. 1228); November 20, 1994 (21:25 Md. R. 1933); July 3, 1995 (22:13 Md. R. 966); January 15, 1996 (23:1 Md. R. 23); April 22, 1996 (23:8 Md. R. 604); August 12, 1996 (23:16 Md. R. 1175); June 30, 1997 (24:13 Md. R. 930); November 3, 1997 (24:22 Md. R. 1551); July 10, 2000 (27:13 Md. R. 1211); February 19, 2001 (28:3 Md. R. 205)

Regulation .01-1A(1) amended as an emergency provision effective July 14, 1999 (26:16 Md. R. 1236); amended permanently effective October 4, 1999 (26:20 Md. R. 1545)

Regulation .01-2 adopted effective October 11, 1993 (20:20 Md. R. 1569)

Regulation .01-2 amended effective June 30, 1997 (24:13 Md. R. 930)

Regulation .02A amended effective October 7, 1996 (23:20 Md. R. 1422); July 10, 2000 (27:13 Md. R. 1211); February 19, 2001 (28:3 Md. R. 205)

Regulation .03B amended effective July 3, 1995 (22:13 Md. R. 966)

Regulation .09 amended effective March 5, 1990 (17:4 Md. R. 496)

Regulation .14G adopted effective October 11, 1993 (20:20 Md. R. 1569)

Regulation .15 amended effective September 3, 1990 (17:17 Md. R. 2078)

Regulation .17A amended effective October 11, 1993 (20:20 Md. R. 1569)

Regulation .17A amended as an emergency provision effective July 14. 1999 (26:16 Md. R. 1237); amended permanently effective October 4, 1999 (26:20 Md. R. 1545)

Regulation .17E amended effective September 1, 1989 (16:16 Md. R. 1749)

Regulation .22B amended effective July 3, 1995 (22:13 Md. R. 966)

Regulation .25B amended as an emergency provision effective July 14, 1999 (26:16 Md. R. 1237); amended permanently effective October 4, 1999 (26:20 Md. R. 1545)

Regulation .26B amended effective July 3, 1995 (22:13 Md. R. 966)

Regulation .27 amended as an emergency provision effective July 14, 1999 (26:16 Md. R. 1237); amended permanently effective October 4, 1999 (26:20 Md. R. 1545)

Regulation .27B amended effective August 5, 1991 (18:15 Md. R. 1725); November 20, 1994 (21:23 Md. R. 1933)

Regulation .27C adopted effective August 5, 1991 (18:15 Md. R. 1725)

Regulation .27C amended effective October 11, 1993 (20:20 Md. R. 1569)

Regulation .28A amended effective June 30, 1997 (24:13 Md. R. 930)

Regulation .31D amended effective November 20, 1994 (21:23 Md. R. 1933)

Regulation .32 amended and recodified to Regulation .01-1 effective October 11, 1993 (20:20 Md. R. 1569)

Regulation .32A amended effective April 16, 1990 (17:7 Md. R. 848)

Regulation .33 adopted effective September 1, 1989 (16:16 Md. R. 1749)

Regulation .33A amended, B repealed effective June 30, 1997 (24:13 Md. R. 930)

Regulation .34 adopted effective June 30, 1997 (24:13 Md. R. 930)

Chapter revised as an emergency provision effective August 10, 2001 (28:17 Md. R. 1551); revised permanently effective November 12, 2001 (28:22 Md. R. 1936)

Regulation .01B amended effective December 12, 2002 (29:24 Md. R. 1919); April 23, 2018 (45:8 Md. R. 419)

Regulation .01-1 amended effective April 19, 2021 (48:8 Md. R. 308)

Regulation .01-1A amended effective September 29, 2003 (30:19 Md. R. 1331); March 17, 2014 (41:5 Md. R. 342)

Regulation .01-1A, B amended effective September 2, 2002 (29:17 Md. R. 1380)

Regulation .01-1A, C amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .01-1B, C amended effective December 12, 2002 (29:24 Md. R. 1919)

Regulation .01-2 amended effective December 12, 2002 (29:24 Md. R. 1919); April 23, 2018 (45:8 Md. R. 419)

Regulation .03B, C amended and D adopted effective September 30, 2002 (29:19 Md. R. 1523)

Regulation .08 amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .09 amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .14 recodified to Regulation .14-1 and new Regulation .14 adopted as an emergency provision effective July 9, 2004 (31:18 Md. R. 1348); adopted permanently effective September 27, 2004 (31:19 Md. R. 1431)

Regulation .14C amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .14D adopted effective April 23, 2018 (45:8 Md. R. 419)

Regulation .14-1G amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .15B amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .16 amended as an emergency provision effective December 22, 2008 (36:2 Md. R. 96); emergency status extended at 36:17 Md. R. 1310; emergency status expired November 19, 2009

Regulation .16 amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .16-1 adopted as an emergency provision effective December 22, 2008 (36:2 Md. R. 96); emergency status extended at 36:17 Md. R. 1310; emergency status expired November 19, 2009

Regulation .16-1 adopted effective December 26, 2011 (38:26 Md. R. 1696)

Regulation .16-1 amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .17 amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .17C amended effective December 12, 2002 (29:24 Md. R. 1919)

Regulation .19 repealed and new Regulation .19 adopted effective April 23, 2018 (45:8 Md. R. 419)

Regulation .27A amended effective September 29, 2003 (30:19 Md. R. 1331); April 23, 2018 (45:8 Md. R. 419)

Regulation .27C adopted effective April 23, 2018 (45:8 Md. R. 419)

Regulation .28 amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .28G amended effective July 16, 2020 (47:14 Md. R. 675)

Regulation .28-1 amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .28-2B, F amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .28-3 amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .29 amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .34 amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .35 amended effective April 23, 2018 (45:8 Md. R. 419)

Regulation .37 adopted effective December 12, 2002 (29:24 Md. R. 1919)

Regulation .38 adopted effective December 12, 2002 (29:24 Md. R. 1919)