# Hydrogen hazard?



## ww321q (Mar 28, 2008)

I would think that you would really have to be cooking the batteries to give off enough hydrogen to blow up . In a confined space the gas will be more apt to build to a rich enough state to be ignited . But in a garage I wouldn't think so . Maybe if your charger sticks wide open max amps and you start to melt down the batteries . Probably more chance of shorted batteries or cables getting hot and catching on fire and burning then an explosion . It may also depend on how much you love your wife  J.W.


----------



## tj4fa (May 25, 2008)

BikerA said:


> My wife is on the second floor of our garage with a propane heater. Is the H emitted during charging an explosion or fire hazard?


Definitely YES!!

The National Electric Code NFPA 70 Article 625 requires among other things an interlocked exhaust fan when charging your EV inside your garage to remove gas vapors.

Any spark or open flame (gas water heater?) can set the hydrogen gas off.

Either back off on the indoor charging until you can check into it further or jack up the life insurance policy on your wife.


----------



## Schmism (Aug 16, 2008)

tj4fa said:


> Definitely YES!!
> 
> The National Electric Code NFPA 70 Article 625 requires among other things an interlocked exhaust fan when charging your EV inside your garage to remove gas vapors.
> 
> ...



the sky is falling the sky is falling.....

H2 requires 4% concentration to ignite. 

some back of the envolope calcs
20x20x8' garage.... =3200cubic ft
4% concentration of 3200cuft = 128 cuft of H2

you know one of those compressed H2 cylinders....










a standard H2 tank is 300cuft. so you'd have to release almost half a tank of H2 in your garage before worrying about blowing up the house.

obviously the smaller the space the less of it you need before it reaches that magic 4% concentration, which is why they recommended venting the trunks/battery compartments.

personally id be more worried about CO poisoning with the propane heater. but suffocating to death never sounds as bad as blowing up.


----------



## ww321q (Mar 28, 2008)

Oh God ! thank you Schmism !!! I think there is a greater danger of the electric system or charger system starting a fire then hydrogen gas blowing up . J.W.


----------



## madderscience (Jun 28, 2008)

Battery charging CAN create enough H2 for a hydrogen explosion:
www.mikeholt.com/documents/safety/pdf/messagefromfiremarshall.pdf

Its true that this example isn't an EV and there are more batteries here than any normal EV has, and it sounds like several things went wrong to cause it, but scale everything down proportionally and a small garage with an EV parked in it and charging for a couple days could do it.

A bigger risk though might be if your EV has unventilated, sealed battery compartments such as a trunk which can capture the gas and concentrate it; and this compartment also has electrical wiring. I put ventilation fans into my car in a couple of places that run when charging and driving to avoid gas buildup.

Short answer, install some ventilation or charge outside. Doesn't need to be a whole lot. an exhaust fan mounted high, or a ridge vent would do it.


----------



## ww321q (Mar 28, 2008)

That stuff ain't that dangerous !!! J.W.


----------



## TX_Dj (Jul 25, 2008)

Just for clarity-

The hindenburg (and other hydrogen-filled dirigibles) did not catch fire due to the hydrogen, but due to the skin that holds the hydrogen in for lift.

If you have a high enough concentration of hydrogen (i.e. sufficient lack of air), then it will not burn. All fuels require some ratio of oxygen in order to burn.

What happened in the case of the hindenburg, is that the skin, which was a flammable porous material was sealed with a flammable material as well. This material was ignited external to the hydrogen resevoir, where air was present to support combustion. Once the fire was started, the structural integrity of the skin was compromised, releasing the pressurized hydrogen gas contained within. Once that fuel was mixed with sufficient oxygen, it was able to sustain flame.

Had the skin of the hindenburg been made of a non-porous, non-flammable material, the chances of that catastrophe would have been far less likely.


----------



## 1clue (Jul 21, 2008)

I agree with that to a point.

The Hindenburg was a frame covered by a skin. I'm not sure what it was, but it was probably the doped fabric that they used on aircraft skins at the time, which is basically gasoline in solid form.

The Hindenburg burned, there wasn't an explosion. It burned from the outside in.

On the other hand, rather than a huge envelope containing gas, it had a large number of gas bladders which were kept inside the frame. From what I understand, there was sufficient room in there for a worker to move around and check things. Which means that in the event of a leaky bladder, there could be the requisite mix of air and hydrogen to support combustion should a spark occur.


----------



## jaspersk (Jun 26, 2008)

tj4fa said:


> The National Electric Code NFPA 70 Article 625 requires among other things an interlocked exhaust fan when charging your EV inside your garage to remove gas vapors.


For anyone interested in reading NEC 625, I am posting a cut and past from pdf. Hopefully, I am not violating any copyright. Please excuse format errors in tables.

ARTICLE 625
Electric Vehicle Charging System

I. General
625.1 Scope. The provisions of this article cover the electrical
conductors and equipment external to an electric vehicle
that connect an electric vehicle to a supply of electricity
by conductive or inductive means, and the installation of
equipment and devices related to electric vehicle charging.
FPN: For industrial trucks, see NFPA 505-2006, Fire
Safety Standard for Powered Industrial Trucks Including
Type Designations, Areas of Use, Conversions, Maintenance,
and Operation.

625.2 Definitions.
Electric Vehicle. An automotive-type vehicle for on-road
use, such as passenger automobiles, buses, trucks, vans, neighborhood
electric vehicles, and the like, primarily powered by
an electric motor that draws current from a rechargeable storage
battery, fuel cell, photovoltaic array, or other source of
electric current. For the purpose of this article, electric motorcycles
and similar type vehicles and off-road, self-propelled
electric vehicles, such as industrial trucks, hoists, lifts, transports,
golf carts, airline ground support equipment,
Electric Vehicle Connector. A device that, by insertion
into an electric vehicle inlet, establishes an electrical connection
to the electric vehicle for the purpose of charging
and information exchange. This device is part of the electric
vehicle coupler.
Electric Vehicle Coupler. A mating electric vehicle inlet
and electric vehicle connector set.
Electric Vehicle Inlet. The device on the electric vehicle
into which the electric vehicle connector is inserted for
charging and information exchange. This device is part of
the electric vehicle coupler. For the purposes of this Code,
the electric vehicle inlet is considered to be part of the
electric vehicle and not part of the electric vehicle supply
equipment.
Electric Vehicle Nonvented Storage Battery. A hermetically
sealed battery, comprised of one or more rechargeable
electrochemical cells, that has no provision for the release
of excessive gas pressure, or for the addition of water or
electrolyte, or for external measurements of electrolyte specific
gravity.
Electric Vehicle Supply Equipment. The conductors, including
the ungrounded, grounded, and equipment grounding
conductors and the electric vehicle connectors, attachment
plugs, and all other fittings, devices, power outlets, or
apparatus installed specifically for the purpose of delivering
energy from the premises wiring to the electric vehicle.
Personnel Protection System. A system of personnel
protection devices and constructional features that when
used together provide protection against electric shock
of personnel.

625.3 Other Articles. Wherever the requirements of other
articles of this Code and Article 625 differ, the requirements
of Article 625 shall apply.

625.4 Voltages. Unless other voltages are specified, the
nominal ac system voltages of 120, 120/240, 208Y/120,
240, 480Y/277, 480, 600Y/347, and 600 volts shall be used
to supply equipment covered by this article.

625.5 Listed or Labeled. All electrical materials, devices,
fittings, and associated equipment shall be listed or labeled.

II. Wiring Methods
625.9 Electric Vehicle Coupler. The electric vehicle coupler
shall comply with 625.9(A) through (F).
(A) Polarization. The electric vehicle coupler shall be polarized
unless part of a system identified and listed as suitable
for the purpose.
(B) Noninterchangeability. The electric vehicle coupler
shall have a configuration that is noninterchangeable with
wiring devices in other electrical systems. Nongroundingtype
electric vehicle couplers shall not be interchangeable
with grounding-type electric vehicle couplers.
(C) Construction and Installation. The electric vehicle
coupler shall be constructed and installed so as to guard
against inadvertent contact by persons with parts made live
from the electric vehicle supply equipment or the electric
vehicle battery.
(D) Unintentional Disconnection. The electric vehicle
coupler shall be provided with a positive means to prevent
unintentional disconnection.
(E) Grounding Pole. The electric vehicle coupler shall be
provided with a grounding pole, unless part of a system
identified and listed as suitable for the purpose in accordance
with Article 250.
(F) Grounding Pole Requirements. If a grounding pole is
provided, the electric vehicle coupler shall be so designed
that the grounding pole connection is the first to make and
the last to break contact.

III. Equipment Construction
625.13 Electric Vehicle Supply Equipment. Electric vehicle
supply equipment rated at 125 volts, single phase, 15
or 20 amperes or part of a system identified and listed as
suitable for the purpose and meeting the requirements of
625.18, 625.19, and 625.29 shall be permitted to be cordand-
plug-connected. All other electric vehicle supply
equipment shall be permanently connected and fastened in
place. This equipment shall have no exposed live parts.

625.14 Rating. Electric vehicle supply equipment shall
have sufficient rating to supply the load served. For the
purposes of this article, electric vehicle charging loads shall
be considered to be continuous loads.

625.15 Markings. The electric vehicle supply equipment
shall comply with 625.15(A) through (C).
(A) General. All electric vehicle supply equipment shall
be marked by the manufacturer as follows:
FOR USE WITH ELECTRIC VEHICLES
(B) Ventilation Not Required. Where marking is required
by 625.29(C), the electric vehicle supply equipment shall
be clearly marked by the manufacturer as follows:
VENTILATION NOT REQUIRED
The marking shall be located so as to be clearly visible
after installation.
(C) Ventilation Required. Where marking is required by
625.29(D), the electric vehicle supply equipment shall be
clearly marked by the manufacturer, “Ventilation Required.”
The marking shall be located so as to be clearly
visible after installation.

625.16 Means of Coupling. The means of coupling to the
electric vehicle shall be either conductive or inductive. Attachment
plugs, electric vehicle connectors, and electric vehicle
inlets shall be listed or labeled for the purpose.

625.17 Cable. The electric vehicle supply equipment cable
shall be Type EV, EVJ, EVE, EVJE, EVT, or EVJT flexible
cable as specified in Article 400 and Table 400.4. Ampacities
shall be as specified in Table 400.5(A) for 10 AWG and
smaller, and in Table 400.5(B) for 8 AWG and larger. The
overall length of the cable shall not exceed 7.5 m (25 ft)
unless equipped with a cable management system that is
listed as suitable for the purpose. Other cable types and
assemblies listed as being suitable for the purpose, including
optional hybrid communications, signal, and optical fiber
cables, shall be permitted.

625.18 Interlock. Electric vehicle supply equipment shall
be provided with an interlock that de-energizes the electric
vehicle connector and its cable whenever the electrical connector
is uncoupled from the electric vehicle. An interlock
shall not be required for portable cord-and-plug-connected
electric vehicle supply equipment intended for connection
to receptacle outlets rated at 125 volts, single phase, 15 and
20 amperes.

625.19 Automatic De-Energization of Cable. The electric
vehicle supply equipment or the cable-connector combination
of the equipment shall be provided with an automatic
means to de-energize the cable conductors and
electric vehicle connector upon exposure to strain that
could result in either cable rupture or separation of the
cable from the electric connector and exposure of live parts.
Automatic means to de-energize the cable conductors and
electric vehicle connector shall not be required for portable
cord-and-plug-connected electric vehicle supply equipment
intended for connection to receptacle outlets rated at 125
volts, single phase, 15 and 20 amperes.

IV. Control and Protection
625.21 Overcurrent Protection. Overcurrent protection
for feeders and branch circuits supplying electric vehicle
supply equipment shall be sized for continuous duty and
shall have a rating of not less than 125 percent of the
maximum load of the electric vehicle supply equipment.
Where noncontinuous loads are supplied from the same
feeder or branch circuit, the overcurrent device shall have a
rating of not less than the sum of the noncontinuous loads
plus 125 percent of the continuous loads.

625.22 Personnel Protection System. The electric vehicle
supply equipment shall have a listed system of protection
against electric shock of personnel. The personnel protection
system shall be composed of listed personnel protection
devices and constructional features. Where cord-andplug-
connected electric vehicle supply equipment is used, the
interrupting device of a listed personnel protection system
shall be provided and shall be an integral part of the attachment
plug or shall be located in the power supply cable not
more than 300 mm (12 in.) from the attachment plug.

625.23 Disconnecting Means. For electric vehicle supply
equipment rated more than 60 amperes or more than 150
volts to ground, the disconnecting means shall be provided
and installed in a readily accessible location. The disconnecting
means shall be capable of being locked in the open
position. The provision for locking or adding a lock to the
disconnecting means shall be installed on or at the switch
or circuit breaker used as the disconnecting means and shall
remain in place with or without the lock installed. Portable
means for adding a lock to the switch or circuit breaker
shall not be permitted.


----------



## jaspersk (Jun 26, 2008)

625.25 Loss of Primary Source. Means shall be provided
such that, upon loss of voltage from the utility or other
electrical system(s), energy cannot be back fed through the
electric vehicle and the supply equipment to the premises
wiring system unless permitted by 625.26.

625.26 Interactive Systems. Electric vehicle supply
equipment and other parts of a system, either on-board or
off-board the vehicle, that are identified for and intended to
be interconnected to a vehicle and also serve as an optional
standby system or an electric power production source or
provide for bi-directional power feed shall be listed as suitable
for that purpose. When used as an optional standby
system, the requirements of Article 702 shall apply, and
when used as an electric power production source, the requirements
of Article 705 shall apply.

V. Electric Vehicle Supply Equipment Locations
625.28 Hazardous (Classified) Locations. Where electric
vehicle supply equipment or wiring is installed in a hazardous
(classified) location, the requirements of Articles 500
through 516 shall apply.

625.29 Indoor Sites. Indoor sites shall include, but not be
limited to, integral, attached, and detached residential garages;
enclosed and underground parking structures; repair and nonrepair
commercial garages; and agricultural buildings.
(A) Location. The electric vehicle supply equipment
shall be located to permit direct connection to the electric
vehicle.
(B) Height. Unless specifically listed for the purpose and
location, the coupling means of the electric vehicle supply
equipment shall be stored or located at a height of not less
than 450 mm (18 in.) and not more than 1.2 m (4 ft) above
the floor level.
(C) Ventilation Not Required. Where electric vehicle
nonvented storage batteries are used or where the electric
vehicle supply equipment is listed or labeled as suitable for
charging electric vehicles indoors without ventilation and
marked in accordance with 625.15(B), mechanical ventilation
shall not be required.
(D) Ventilation Required. Where the electric vehicle supply
equipment is listed or labeled as suitable for charging
electric vehicles that require ventilation for indoor charging,
and is marked in accordance with 625.15(C), mechanical ventilation,
such as a fan, shall be provided. The ventilation shall
include both supply and exhaust equipment and shall be permanently
installed and located to intake from, and vent directly
to, the outdoors. Positive pressure ventilation systems
shall be permitted only in buildings or areas that have been
specifically designed and approved for that application. Mechanical
ventilation requirements shall be determined by one
of the methods specified in 625.29(D)(1) through (D)(4).
(1) Table Values. For supply voltages and currents specified
in Table 625.29(D)(1) or Table 625.29(D)(2), the minimum
ventilation requirements shall be as specified in Table
625.29(D)(1) or Table 625.29(D)(2) for each of the total
number of electric vehicles that can be charged at one time.
(2) Other Values. For supply voltages and currents other
than specified in Table 625.29(D)(1) or Table 625.29(D)(2),
the minimum ventilation requirements shall be calculated
by means of the following general formulas as applicable:
(1) Single phase: Ventilation single phase in cubic meters per
minute (m3/min) =
volts amperes
1718
( )( )
Ventilation single phase in cubic feet per minute (cfm) =
volts amperes
48.7
( )( )
(2) Three phase: Ventilation three phase in cubic meters per
minute (m3/min) =
1 732
1718
. (volts)(amperes)
Ventilationthree phase in cubic feet per minute (cfm) =
1 732
48 7
.
.
(volts)(amperes)
(3) Engineered Systems. For an electric vehicle supply
equipment ventilation system designed by a person qualified
to perform such calculations as an integral part of a
building’s total ventilation system, the minimum ventilation
requirements shall be permitted to be determined per calculations
specified in the engineering study.
(4) Supply Circuits. The supply circuit to the mechanical
ventilation equipment shall be electrically interlocked
with the electric vehicle supply equipment and shall remain
energized during the entire electric vehicle charging cycle.
Electric vehicle supply equipment shall be marked in accordance
with 625.15. Electric vehicle supply equipment receptacles
rated at 125 volts, single phase, 15 and 20 amperes shall
be marked in accordance with 625.15(C) and shall be
switched, and the mechanical ventilation system shall be electrically
interlocked through the switch supply power to the
receptacle.

625.30 Outdoor Sites. Outdoor sites shall include but not
be limited to residential carports and driveways, curbside,
open parking structures, parking lots, and commercial
charging facilities.
(A) Location. The electric vehicle supply equipment shall be
located to permit direct connection to the electric vehicle.
(B) Height. Unless specifically listed for the purpose and
location, the coupling means of electric vehicle supply
equipment shall be stored or located at a height of not less
than 600 mm (24 in.) and not more than 1.2 m (4 ft) above
the parking surface.
ARTICLE
Table 625.29(D)(1) Minimum Ventilation Required in Cubic Meters per Minute (m3/min)
for Each of the Total Number of Electric Vehicles That Can Be Charged at One Time
Branch-
Circuit
Ampere
Rating
Branch-Circuit Voltage
Single Phase 3 Phase
120 V 208 V
240 V or
120/240 V
208 V or
208Y/120 V 240 V
480 V or
480Y/277 V
600 V or
600Y/347 V
15 1.1 1.8 2.1 — — — —
20 1.4 2.4 2.8 4.2 4.8 9.7 12
30 2.1 3.6 4.2 6.3 7.2 15 18
40 2.8 4.8 5.6 8.4 9.7 19 24
50 3.5 6.1 7.0 10 12 24 30
60 4.2 7.3 8.4 13 15 29 36
100 7.0 12 14 21 24 48 60
150 — — — 31 36 73 91
200 — — — 42 48 97 120
250 — — — 52 60 120 150
300 — — — 63 73 145 180
350 — — — 73 85 170 210
400 — — — 84 97 195 240
Table 625.29(D)(2) Minimum Ventilation Required in Cubic Feet per Minute (cfm)
for Each of the Total Number of Electric Vehicles That Can Be Charged at One Time
Branch-
Circuit Ampere
Rating
Branch-Circuit Voltage
Single Phase 3 Phase
120 V 208 V
240 V or
120/240 V
208 V or
208Y/120 V 240 V
480 V or
480Y/277 V
600 V or
600Y/347 V
15 37 64 74 — — — —
20 49 85 99 148 171 342 427
30 74 128 148 222 256 512 641
40 99 171 197 296 342 683 854
50 123 214 246 370 427 854 1066
60 148 256 296 444 512 1025 1281
100 246 427 493 740 854 1708 2135
150 — — — 1110 1281 2562 3203
200 — — — 1480 1708 3416 4270
250 — — — 1850 2135 4270 5338
300 — — — 2221 2562 5125 6406
350 — — — 2591 2989 5979 7473
400 — — — 2961 3416 6832 8541


----------



## dtbaker (Jan 5, 2008)

interesting code. I had no idea such a thing existed! 

Anyway..... in my case, the rear battery box is passively vented with some holes near the top (NOT into the cabin) and a hole near the bottom. There are NO wires other than battery cables in the box, so no opportunity for sparks. Once into the garage, it is a 2 car garage, with typical passive vents near the fllor and poorly fit doors that let in a lot of air if there is any wind at all. There are NO water heaters or sources of open flame or spark in the garage. I charge on 110v house current, 12 amp max. 

In reading the code, I am wondering if you can also paste in the sections stating the specific conditions for when labelling and venting must occur as referenced by:

(B) Ventilation Not Required. Where marking is required
by 625.29(C), the electric vehicle supply equipment shall
be clearly marked by the manufacturer as follows:
VENTILATION NOT REQUIRED
The marking shall be located so as to be clearly visible
after installation.
(C) Ventilation Required. Where marking is required by
625.29(D), the electric vehicle supply equipment shall be
clearly marked by the manufacturer, “Ventilation Required.”
The marking shall be located so as to be clearly
visible after installation.


----------



## fugdabug (Jul 14, 2008)

BikerA said:


> My wife is on the second floor of our garage with a propane heater. Is the H emitted during charging an explosion or fire hazard?


hmmmm... better safe than sorry. vent it.


----------

