Couple: $20.00 per year
Family: $30.00 per year
Points: $20 per class per year
Hooks: Members is $10.00 per class
Non–Members is $20.00 per class (Limit of 2 pulling events)
1. Total weight of the classes includes vehicle, driver seated, helmet, eye protection, neck brace, shoes, fire suit, jacket and/or pants. Eye protection includes; safety goggles, safety glasses or prescription eyeglasses.
2. All tractors may enter in two (2) classes per event only.
3. Tires: no studs, chains, or duals are permitted.
4. All power must be transmitted through the rear wheel only, no four wheel drives.
5. Must have a 2” number on the front or both sides of tractor. Numbers will be assigned to tractors.
6. Hitch can be adjustable but must be locked at 13” maximum.
7. All pullers must be a registered member of the Lena Mini and Modified Tractor Pullers Association.
8. First puller disqualified there will be NO re-pull. First puller out of bounds will get a re-pull. First puller that re-pulls will be last in that class.
9. Mechanical problems: 10 minutes from time you are unhooked and pushed away from eliminator. Tractor can re-hook anytime during that class.
10. If a tractor is bought or sold during the pulling season, the points will start at zero (0) for the new owner. Previous owner retains points for the season earned to date of sale. Points money will be paid out at club banquet to each owner for the year.
11. MEMBERSHIP MUST BE PAID TO VOTE AT MEETINGS AND AT PULLS.
12. All tractors must join points and membership at clubs third (3rd) pulling event.
13. 75 foot shut down, 2nd pull counts – must adjust weights.
14. All tractors can be checked at any time by President and Vice President’s discretion.
15. The Board of Directors has the right to change any rules, at any time, when it involves safety.
16. UTV’s and ATV’s in pits – Driver’s License or proof of ATV safety course required to drive.
17. All tractors must have working brakes.
18. RAINOUTS: All registered pullers in that class will get 1 show point PLUS first place points based on number of registered tractors in that class.
19. TECH DAYS: If tractor is not teched by the second tech date—tractor gets -5 points before season begins.
20. A capable driver must be seated in vehicle when the engine is being started, and whenever it is running. Drivers must have complete control at all times.
21. TIME LIMIT RULE: Puller has 3 minutes from the time eliminator is ready to hook up at the staging area. Track official for that eliminator is in charge of time keeping.
22. ANY RULE INFRACTION/S will result in loss of points and/or monies for that day, for that class. Also consideration of suspension from competition for 1 year and 10 days from date of infraction by vote from Board of Directors.
23. Rear weights 24 inch maximum length, center of rear axle to furthest point back.
1. All drivers must wear a correctly fitting DOT approved helmet while on the track. Helmet must be fastened when pulling. Loss of helmet is a disqualification.
A: Mini rods need a full face helmet. (Please see rules regarding eye protection.)
2. Eye protection is required. If NOT wearing eye protection, helmet shield MUST be down.
If wearing eye protection, helmet shield IS NOT required to be down.
3. Mini rod classes need to use a neck brace (horse collar) support.
4. Long pants and closed toe shoes (no slip-ons) are required in all classes.
5. Fire jackets are required in pro-stock, modified, and outlaw classes.
A: Fire jackets and fire pants are required for mini rods.
6. Mods, outlaws and mini rods are required to have a fire extinguisher mounted in reach of the driver.
7. Wheelie bars are required in all classes. Devices must be made of two separate sections, one on each side at rear of tractors. Each device must be ridge mounted and equipped with skid plates or wheels at ground contact point. Skid plates must be at least three inches square or wheels shall be at least one inch wide and four inches in diameter. Wheels or skid plates are to be at least five inches behind face of rear tires and no more than five inches above ground. The combination of both wheelie bars must be strong enough to support entire weight of driver and tractor when jack is placed under them and tractor is raised. No spring loaded anti-tip devices are allowed.
8. No driver will be allowed to consume alcoholic beverages or use drugs before they pull or are done loading their tractor. If a driver is considered under the influence, that driver will be banned for one year from the date of infraction. No points will be given to the tractor that day.
9. No unsportsmanlike conduct, use of profanity or disorderly conduct will be tolerated. Offenders will be asked to remove themselves from the pulling grounds immediately. No points will be given to the tractor that day. Disciplinary action will be left to the discretion of the Board of Directors.
10. NO BOUNCING! Drivers must remain seated at all times. If you leave your seat, you will be disqualified at the track officials’ discretion. One hand on the steering wheel at all times.
11. Pro-stock, modifies and outlaw classes are required to fully enclose all fly wheel, clutches, and chains 360 degrees with a minimum 1/8 inch thick steel or equivalent. Flywheels and starter pulleys made of steel and aluminum, no cast iron or cast aluminum. All pulleys and belts must be shielded at least the width of the pulley with a .060 thick steel or equivalent. No welded flywheel fins or stamped steel pulleys will be allowed. Starter pulleys must have a retaining device to prevent the pulley from coming off crankshafts. U-joints used in drivelines must be shielded 360 degrees with ¼ inch thick aluminum or 1/8 inch steel.
12. Loose anything on the track that DOES NOT STOP your tractors movement or safety equipment—YOU ARE DISQUALIFIED.
13. If any BREAKAGE OCCURS on the track that STOPS your tractors movement – you get distance measured.
14. All non-stock vehicles must be equipped with a working pullout type switch disconnecting power to both the ignition and any electric fuel pump. Switch to be rear mounted within 6’ of the center of the vehicle. Diesel engines must have air shutoff, which is mechanically operated and prevents building boosts. Diesel tractors must also have a fuel shutoff located within easy reach of the driver.
15. All vehicles must have a securely attached seat with at least a 3” high seat back.
16. All throttles other than stock classes must be spring return to idle. Hand throttles must push forward to increases rpms.
17. No pressurized fuels or fuel tanks of any kind.
18. All vehicles must be equipped with rear fenders extending at least 4” horizontally over the rear wheels.
19. All exhaust must discharge upwards.
20. No hot rodding onto or off of the track or in the pit area.
21. All pullers under 18 years of age must have a waiver sheet signed by a parent or guardian before competing.
22. Fire extinguisher required in all classes.
23. If the idle is up when leaving the track and tires spin, throwing dirt, the contestant will be disqualified.
24. President and/or Vice-President can bar from competition any vehicle, at any time, which they believe has a potential safety problem.
25. Mini rods must be equipped with a neutral safety starter switch on the gearshift, which will allow starter engagement only in the neutral or park position. Safety switch on clutch.
26. Mini rods must have a 2 inch diameter white light on the back of tractor that automatically goes on when the vehicle is put in reverse.
27. Mini rods drivers must put both hands up while hooking and unhooking tractor.
28. DRIVER ONLY on pulling tractor!
29. Driver is not allowed to hold onto the outside edges of fenders with either the right or left hand. Failure to do so will result in disqualification.
30. First puller is test puller. If eliminator gets changed, first puller goes to the end of the class. Any repull (turned down) tractor goes to the end of the class.
31. Eliminator can be moved anywhere in the box before eliminator backs in the box. If eliminator does not move 75 feet, next puller can have eliminator moved to a new position within the box. This will count as an attempt.
32. Once tractor has gone over the scale and in staging area, no air, gas, or anything that would change tractor weight or hitch height may be added. If tractor leaves staging area to add air to tires, or transfer/add gas, or perform anything that would change tractor weight or hitch height, puller must have a track official accompany puller to observe and witness transaction and tractor must again cross the scale before returning to the staging area.
1. If a competitor breaks in the previous class, and cannot make the pull order in the next class, puller must notify the track official for the need of extra time. The track official must allow that puller to drop to the last pulling position.
Eligibility of Contestants:
1. All competitors must hold a current competition membership.
2. Contestants must be 18 years of age, or at least 16 years of age with a written permission from a parent or guardian, with modified experience and Board of Director’s approval to pull or drive tractor in pit area.
1. Registration means identifying the pulling vehicle with a registration number for point’s calculation. All tractors must be registered before competing. The number must be displayed on both sides of the tractor with minimum 2” numbers in a visible location.
2. If 2 or more people own a tractor, they must use the same registration number. In order to be a driver each person must have a current competition membership.
3. All tractors must pass a tech inspection before competition.
4. If registered for 2 classes and tractor breaks when pulling in the first class and not able to pull in your second class, you will get 1 show point in the second class.
5. After registration is CLOSED…NO SCRATCHING from a class, NO REFUNDS, NO POINTS. (Exception : Family emergency and you have to leave event, then at President’s discretion.) Please also refer to Entry Positions: Rule 1. *****************************************************************************
0-12 H.P. 750# Kids (5 to 12 years old only) Kids must be tethered to an adult or guardian of 18 years old and meet all rules.
HORSEPOWER WEIGHT TIRE
0-12 HP 850# Turf
0-12 HP 950# Turf
0-18 HP/1 cylinder only 1050# Bar
0-20 HP 1100# Turf
0-20 HP 1150# Turf
0-25 HP 1050# Bar
0-25 HP 1200# Bar
1. Bar tire class can pull with bar tires or turf tires with a MAXIMUM size of 26x12x12.
2. Must be stock stroke, .030 overbore maximum. Stock compression, stock camshaft, stock small engine carburetor, and stock valves. Technicians have option to check engine.
3. Front weights 24 inch maximum length, from front axle forward to furthest point.
4. Hitch height—maximum 13 inches to middle or top of the hitch and compatible to hook. It cannot interfere with the chain.
5. Governors maybe unhooked, no maximum RPM’s
6. Any exhaust other than stock must extend upward.
7. Mower decks allowed.
8. 75 foot shut down. 2nd pull counts and you must adjust weights or you will get disqualified.
9. Must have stock wheel base.
10. Must have wheelie bars.
11. Billet/Steel Flywheel-with NO RPM limit, stock shield.
12. Cast Flywheel-with NO RPM limit, MUST have a 3/16″ steel or 1/4″ aluminum shield from frame rail to frame rail within a half (1/2) inch of original shield and mounted solidly.
13. Cast Flywheel-with stock shield only, 3800 RPM’s maximum.
14. Must have a stock appearing hood and grill for make and model of the lawnmower.
15. No injection of any kind other than if it is stock for that engine.
1. Must run stock factory hood.
2. Stock fenders.
3. Stock chassis-may have tube inside of chassis, but must remain stock appearing outside.
4. Any rear end combination allowed.
5. Jackshafts allowed.
6. 72-inch length, center of rear axle to furthest point forward.
7. 13 inch hitch height maximum. Measured to the top or middle of the hitch. Hook point to center of rear axle minimum 6 inch.
8. All drive shafts and drive chains must be shielded.
9. 25x12x12 maximum tire size. Tires may be cut, they must be 4 ply maximum. ATV or turf tires only.
10. 48-inch rear wheel width maximum, outside to outside.
11. Must have wheelie bar.
12. Kill switch mandatory.
13. 400cc maximum. Single cylinder 2 or 4 stroke.
14. Rear weights 24 inch length, center of rear axle to furthest point back.
15. Must have working brake.
16. Gas only, NO alcohol.
17. Minimum of 2 years of pulling with the LMMTPA club and/or Board of Director’s permission.
18. 75 foot shut down. 2nd pull counts – must adjust weight.
19. No injection of any kind other than if it is stock for that engine.
875# PRO-STOCK II
ALL THE SAME RULES AS 825# EXCEPT:
1. 2 cylinder maximum 600cc Four stroke 440cc Two stroke
2. Due to the projected number of Pro Stock entries, less than 3…we will be allowing the 825/875 Pro Stock tractors to run with the 13-16 HP Single Cylinder (1050) class. Bar tires will be allowed.
Please note: This rule will be re-evaluated after second tech day and/or seasons end by Board of Directors.
|Weight Class||2 Cycle||4 Cycle|
1. Production motorcycle, snowmobile engines only. Maximum 4 cylinders, all motors combined. Total displacement not to exceed class limit.
2. Maximum of 4-venturi carbonation combined total. Fuel injection only if stock for that engine. Gasoline or racing gas only. NO ALCOHOL.
3. Engines must be naturally aspirated. No turbochargers or superchargers allowed.
4. Maximum tire size 26-12.00×12.
5. Maximum wheelbase-96 inches. Maximum overall length from the center of the rear axle forward-102”. Maximum width-60”. Maximum overall length forward of the centerline of the front axle is 24” excluding the front tow hitch.
6. Automotive rear axle/differentials are allowed as well as solid rear axles.
7. Sheet metal in modified divisions is optional. All driveshafts and chains must be shielded.
8. Hitch height maximum 13 inches to top or middle and a minimum of 6 inches behind the center of the rear axle.
9. Minimum of 16 years of age or minimum of 2 years pulling experience in the LMMTPA club and/or approval of the Board of Directors.
10. Fire extinguisher is required.
11. Kill switch mandatory.
12. Must have wheelie bars and working rear brake.
13. 75 foot shut down. 2nd pull counts – must adjust weight.
14. No steel flywheel.
15. No injection of any kind other than if it is stock for that engine.
Weight Class 2 Cycle 4 Cycle
1450# 1800cc 2500cc
1500# 1800cc 2500cc
1. Engines must be naturally aspirated. No turbochargers or superchargers.
2. Maximum tire size 26-12.00×12.
3. Hitch height maximum 13 inches, to top or middle, and a minimum of 6 inches behind the center of the rear axle.
4. Fire extinguisher is required.
5. Kill switch mandatory.
6. Must have wheelie bars.
7. Must have working rear brakes.
8. Minimum of 16 years of age or minimum of 2 years pulling experience in the LMMTPA club and/or approval of the Board of Directors.
9. No limit on cylinders.
10. Sheet metal is optional. All drive shafts, universal joints and chains must be shielded.
11. Tractor is not to exceed 72 inches wide and maximum overall length of 120 inches.
12. Roll cage and three-point harness is recommended on all new tractors.
13. Automobile style rear axle/differentials allowed as well as solid rear axle.
14. 75 foot shut down. 2nd pull counts – must adjust weights. 1
5. No injection of any kind other than if it is stock for that engine.
LMMTPA Mini Rod Class Rules
IN ADDITION TO “GENERAL” RULES!
Official Weight Classes
1900lbs and 1950lbs
1. Engines must be naturally aspirated. No turbochargers or superchargers.
2. Maximum tire size 18.4 x 16.1.
3. Hitch height maximum 13 inches, to top or middle, and a minimum of 6 inches behind the center of the rear axle.
4. Minimum of 16 years of age or minimum of 2 years pulling experience in the LMMTPA club and/or approval of the Board of Directors.
5. Maximum of 8 cylinders.
6. Sheet metal is optional. All drive shafts, universal joints and chains must be shielded.
7. Roll cage and three-point harness are mandatory.
8. Automobile style rear axle/differentials allowed as well as solid rear axle.
9. No fuel injection of any kind.
10. Motors will be 434 cubic inch with no + (plus) tolerance.
1. Drawbar height to be a maximum of 13” at the inside back of the hole (hook point).
2. Drawbar must have a minimum of 1-1/2” diameter hole.
3. No portion of the tractor may interfere with the sled, chain, or hook during a pull, or while being hooked or unhooked.
4. Drawbar hitching point bolt must be a min. of a ½” bolt, grade 8.
5. 1 inch minimum solid steel drawbar is required with a minimum 1-1/2 inch hole with 1 inch maximum to 3/4 inch minimum from hook point to back edge.
6. Drawbar must be a minimum of 6” long to hook point from the center of the rear axle, with a maximum of 18” long to hook point.
7. Wheelie bars are to be separate from the drawbars.
1. Wheelie bars are to be a maximum of 6” off the ground, minimum of 5” from the vertical rear of the tire, with 2 bars that have a minimum of a 3” x 3” pad, or a 1” x 5” solid centered wheel, and be able to support the weight of the tractor.
2. Mini rods must have bumper bars. Specs will be the same as the NTPA rules.
3. In addition to stabilizer bars, there must be a brace that extends vertically 6 inches from the rear most tip of skid pads.
4. There must be a support brace extending inward to frame, axle, or top of stabilizer bar arms.
5. Vertical brace should extend rearward a minimum of 2 inches from radius of rear tire.
6. Material used to build vertical brace and support brace must be the same size and strength as the material used to build stabilizer bar.
7. Front skid on front axle is 1 1/2” wide and 6” long. Must be 1” below bottom of spindle.
Flywheel and Clutch Shielding:
1. Flywheel and clutch must be wrapped 360 degrees with S.E.M.A. approved bell housing, S.E.M.A. approved safety blanket, ¼ inch aluminum or 3/16 inch steel.
2. All automatic transmissions must be covered with S.E.M.A. approved safety blanket and/or shield.
3. MANDATORY: The bell-housing must be covered with a S.E.M.A. approved flywheel flex plate shield, or a steel shield that is 3/16” thick by 3” wide.
4. No cast iron flywheels.
1. All tractors shall have wide front axles. Front wheels shall track within rear wheels.
2. No portion of any tractor shall exceed 8 foot forward of the center of the rear wheels, except for the tow ring.
3. No portion of any tractor shall exceed 6 feet in width.
(3a.) Tread width (footprint) not to exceed 6 feet in width. Per NTPA rules 2007 page 56(Effective 3-1-12)
4. Tractor must be equipped with a roll-cage which must be at least .095 or 13 gauge mild steel thickness.
5. Roll cage must consist of at least 2 bars down each side, connected across the top, and 2 bars down the back.
6. Roll-cage must be secured with a minimum of (4) four Grade 8 – 3/8″ bolts or welded to frame.
7. Minimum 3 point harness seat belts are required.
8. Battery mounted on outside of frame rail must be securely mounted, no bungee straps/cords.
Engines: No Big Blocks
1. All tractors require side plates the length of the engine block, 6” above and below the crankshaft centerline, made of 1/8” aluminum or 1/16” steel.
2. Side shields must be mounted independently of the engine block.
3. All blow tubes must exit forward of the rear wheels.
4. All pulling tractors must be equipped with mechanical throttle linkage with return to idle springs. No Hydraulic throttle linkages are allowed. All foot throttles must have toe straps.
5. All fans and stock type harmonic balancers must be wrapped 360 degrees with 3/16” steel or 1/4” aluminum, and with a crossbar on the front.
6. One-piece harmonic balancers and SFI approved harmonic balancers must be bolted to the crank with a minimum grade 8 bolt.
7. All exhaust must discharge vertically and be securely attached. Vertical is defined as being within 30 degrees, in any direct of being plumb.
8. No rain caps. 9. 2 bolts with 1/8 inch hole in the oil pan.
1. NO alcohol or any forms of Nitromethane, including Nitrous Oxide, are illegal as fuel or fuel additives for pulling. Gasoline or racing fuel only. If any competitor is proved for use of illegal fuel, the penalty will be loss of all points and suspension of membership for one year and 10 days.
2. No pressurized fuel tanks are allowed.
1. All pulling vehicles must have a breakaway ignition kill switch in working order at all times.
2. The breakaway kill switch must be mounted in the rear, independent of the drawbar.
3. The breakaway kill switch must break current or ground the ignition circuit as necessary to disrupt ignition to the engine(s). On vehicles equipped with electric fuel pump(s), the switch must also break the current to the fuel pump(s).
4. All ignition engines must have another kill switch in working order, mounted within easy reach of the driver.
5. Kill switch will be tested at scale.
1. All driveshaft must be covered 360 degrees with ¼” steel or 3/8” aluminum.
2. All chains must be covered 360 degrees with 1/16” steel or 1/8” aluminum.
Seats and Fenders:
1. All seats must have a minimum of a 6” high back.
2. Fenders are to consist of a barrier between the driver and tire. Fenders are to extend a minimum of 4” horizontally from the inside vertical edge of the tire.
Super Chargers and Turbo Chargers:
1. NO superchargers or turbochargers are allowed in any class
1. Tire size up to: 18.4-16.1
2. Contest is open to pulling vehicles with rubber tires. NO four-wheel drive. NO dual tires, tire studs, or chains. All power must be transmitted through the rear wheels.
Mini Rod Limitations
1. Maximum of 434 cubic inches with NO + (PLUS) TOLERANCE.
2. All tractors must use OEM transmissions.
3. No aluminum blocks. Cast iron only.
4. No aftermarket four valve per cylinder heads or aftermarket aluminum blocks.
5. No turbine engines.
6. Any mini rod can be checked at any time by President and Vice President’s discretion. ******************************************************************************
Mini Rod Protest Rule: Tri-County’s basic rule
A $300.00 cash tear down fee must accompany any written protest from person in same class, as to the legality of a competitors motor within 15 minutes of class ending delivered to President or Vice President of the club. Fifty ($50) dollars of the fee will become property of the club and is not refunded. The tractor will be checked for legal camshaft, engine sealed by two (2) bolt at the end of event by President and/or Vice President. The time and place of teardown will also be determined. If the tractor is found to be legal, the protestor will forfeit his/her remaining $250.00 to the owner of the tractor. If the tractor is found to be illegal, the protestor will get his/her $250.00 returned. Any tractor owner refusing the teardown of their motor will be automatically be declared illegal. Penalty for being disqualified for running an illegal engine is: The tractor will be banned from competing with the Lena Mini and Modified Tractor Pullers Association for one year and 10 days.
Pro Stock Compact Diesel Tractor Division:
- All tractor general rules and safety rules for the Open Division apply except as noted below. All tractors must have a roll cage. All drivers must wear four point harness, neck brace, full faced helmet with eye protection as described above.
- Maximum weight 2100 lbs.
- Single engine with a maximum of 250 cubic inches
- This class is for stock appearing tractors with full hood, grill and side panels. Must be recognizable as an actual modern production compact tractor or small farm tractor. Hood and grill can be from a different make than engine/frame/rear end.
- Engine must be compression ignition and use #2 Diesel Fuel* only. No spark plugs or alcohol as a fuel.
- Hitch height up to 15 inches allowed
- Engine must be commercially produced with at least 1000 units built. Engine block must have factory casting model and serial numbers visible. O.E.M. block cannot be altered in any way externally except for normal repair or for mounting fuel injection pumps.
- Maximum of 4 cylinders
- May be liquid or air cooled.
- No belt driven cooling fans. Electric fans only.
- O.E.M. head for that make/model engine only. No billet or aftermarket heads. No overhead cams. Maximum of 2 valves per cylinder. Injectors must remain in stock location.
- No billet injector pumps. No electronic or common rail injection systems.
- Tractors are allowed a single (1) turbo charger with any manifold modifications necessary to mount the turbocharger. Manifold pressure must be a single stage only.
- Turbocharger must be single shaft fixed vane type. No variable vane turbochargers allowed. No inlet or outlet size restrictions.
- Turbo must be fitted with a shutdown guillotine on the compressor inlet side of the turbo.
- Turbochargers not under the hood will be completely shrouded with steel .060” or thicker, except for inlet and exhaust pipes. Turbochargers under fiberglass hoods must be shrouded, except for the inlet and outlet pipes, with .060” steel or thicker under the area of the fiberglass.
- No wastegates or pressure reliefs of any kind permitted. All compressed air is to enter the intake manifold.
- All turbocharged engines are required to have one cable that must surround the engine block and head. This cable shall be located between the first and second cylinder through the exhaust manifold port area. The cable will be a minimum of 5/16” thick with two (2) clamps at the splice. The cable should allow for approximately 4” of slack.
- Water injection will be allowed. Must be plain water or water with water soluble lube only. Combustible agents (alcohol, oxygenators, etc.) are NOT allowed in water injection.
- No intercoolers or after coolers
- No propane, nitrous injection or any type of secondary fuel system of any kind will be permitted.
- Any stock appearing frame rail or tube frame is permitted. Tube frame must be covered with sheet metal.
- Full metal side panels to cover engine area. Minimum .060” steel or aluminum
- All inline engines are required to have an additional inner side shield consisting of .125” (1/8”) thick steel or titanium OR .250” (1/4”) aluminum inside of the current .060” steel or aluminum side panels with a minimum of .500” (1/2”) air gap. This shield is to be independent of the side panels and must be solidly attached at the top and bottom (4 point total minimum) with a minimum of 5/16” fasteners. This shield must extend from the bottom of the head to the centerline of the crankshaft and extend the full length of the block on each side of the engine.
- All tractors must have a fuel shut-off AND an air shut off mounted in the drivers’ compartment and within reach of the driver. Fuel shut off must return fuel to tank or loop back to pump.
- Kill switch device mounted on rear of tractor must disconnect power to the electric fuel pump along with activating turbocharger guillotine.
- Clutch and bell housing rules to be the same as the EconoMod division
- Automatic transmission shielded with 3/16” steel or 6 belt blanket from end of block to tail shaft. All other block adapters shielded by 3/16” steel the width of the adapter.
*Diesel only with a dielectric value of no greater than 4.9 or less than 2.2
The dielectric meter shall use Cyclohexane to establish zero reference point in determining all diesel fuel dielectric constant values. The use of additives containing oxygen, such as nitro methane, propylene oxide, dioaxane, MTBE, alcohol (methanol, ethanol etc.) or nitrous oxide is prohibited.