H2S

Hydrogen Sulphide gas:

Hydrogen Sulphide gas is one of the most deadly

occupational hazards in drilling. It goes by many names:

H2S, Sour Gas and Sulfuretted Hydrogen.

People working in the oil and gas industry must be aware

of its deadly properties. Sewer maintenance crews,

blasters and miners have learned to respect this gas.

Employers must ensure that workers who may be exposed

to H2S gas are able to recognize its lethal effects. Workers

should also know how to rescue and administer first aid to

victims who are overcome.

The purpose of this section of the site is to alert employers

to the dangers involved in working with H2S and to

provide guidance for controlling those dangers and to give

confidence while working in affected areas such as the Far and Middle East and parts of Canada

The objective of this site is not to teach old dogs new

tricks, most major operator are well familiar with the dangers of H2s and have all there plans in place.

The industry is changing. Over the past 12 years I have

worked for many small indigenous companies. Many are new to the oil industry and some have much to learn.

It is our responsibility to continue to train others.

Hydrogen-Sulphide (H2s) is a gas encountered all over the

world. Drilling formations with the presence of H2S can

encounter some very serious problems.

This section we will attempt to cover the characteristics,

detection, prevention, emergency procedures, safety and

first aid, and training and planning. Due to the serious

nature of this gas, coupled with fear and sometimes

disrespect. We will attempt to get a clear understanding.

Introduction

However before starting I will tell a short but true story.

Some years back "Not that many" we were drilling a

known H2s area. After tripping for the bit, drilling

continued. As one would expect bottoms up eventually

came to surface, along with it came a lot of H2s. Constant

drills had taught everybody to masks up at the first

indication and of course this was done.

However not everyone understood what was going on.

From the time the rotary stopped turning until the time

the rig was secure, the rig floor telephone never stopped

ringing. Once I answer it, I cant understand a word your

saying take your mask "off" A slip up such as that could

cost a person their life.

I have never believe in the Dog eat Dog attitude or the

F*** U Jack I'm all right approach. But under H2s

conditions It MUST be the attitude you take. As much as I

hate to say it. If your best friend is laying out there. You do not go and assist until you are masked up.

TERMINOLOGY:

PPM means (Parts Per Million) and is used for the so-called

toxic gases such as Hydrogen Sulphide and Carbon Monoxide.

These two gases require separate sensors because their lethal

concentrations are so different - H2S is deemed dangerous

above 10ppm (UK) or 15 ppm (US) whilst CO may be

survivable at over 200ppm although most monitors will alarm at only 35ppm (US) 50ppm (UK).

It is surprising to many to learn that a fundamental gas like

methane will not explode in the presence of a flame until it

reaches a very specific concentration - below a certain level

the gas is deemed too lean to burn and above a certain limit

the gas may be too rich to burn rather like smothering a fire

with too much wood.

But within what may be a narrow band, between the Lower

Explosive Limit (LEL) and the Upper Explosive Limit

(UEL) such gases will ignite with only the faintest whiff of a

Zippo.

Other gas related terms are:

TLV: (Threshold Limit Value) & TWA (Time Weighted

Average) both are referring to the duration of exposure to a

particular atmosphere. TWA usually refers to an 8 hour working day over a 40 hour week. TLV will include this

definition but also defines two other exposure limits - Short

term or 15minute exposure and an absolute limit or ceiling

which is the most that an individual should ever be exposed

to.

PEL is the (Permissible Exposure Limit) and this is a

figure defined by the OSHA (US equivalent of HSE in the UK)

as the legal limit of exposure for an employee. This means

that they may be knowingly exposed to a known hazardous

gas for no longer than a legislated maximum time. Any

exposure beyond the PEL for that particular gas and the

bereaved relatives can presumably sue.

STEL: is a UK term meaning (Short Term Exposure Limit)

and refers to a maximum concentration or percentage

exposure over a 15 minute period (similar to TLV-Short Term

above)

IDLH means (Immediately Dangerous to Life or Health)

and is not something you want to see next to a low number on

a Permit before making an entry. This is because IDLH given

as a percentage or PPM represents the maximum exposure

level at which you could survive for 30 minutes without

breathing apparatus and without incurring debilitating symptoms which would hinder your escape or even irreversibly

damage your health. Thus if a gas is given an IDLH of 1ppm or

.000001% you know that it's a nasty one and if your SCBA

packs up when your monitor is showing 10ppm its Goodnight

Vienna.

Properties of H2S

Color: Colorless (Invisible.)

Odour commonly referred to as Odour of rotten eggs

Vapour density 1.189 (Air=1.0) H2S is heavier than air

Explosive limits Highly explosive. (4.3 to 46.) Percent by

volume in air

Auto ignition temp. 260 degrees C Flammability Forms explosive mixture with air or oxygen

Water solubility 2.9 percent (2.9g/100 ml water at 20 degrees

C

Can destroy steel and rubber seals very quickly.

Effects of H2S

10,000 parts per million = 1 percent

1 ppm: Can be smelled. or to put it another way, 1 second in

13 days. Not a lot of room for error.

10 ppm: Occupational Exposure Limit, for 8 hours: At very low concentrations of less than 10-100 ppm, it gives off

unpleasant odour - like to rotten eggs. "The threshold limit".

15 ppm: Occupational Exposure Limit, allowable for 15

minutes of exposure.

20 ppm: Occupational Exposure Limit, At this level workers

must wear appropriate breathing apparatus.

The limits here are set in Canada and conform very much to many other countries

100 ppm: the gas kills the sense of smell in 3-15 minutes and

will cause you to cough or your eyes to water, possible

headache, nausea, throat irritation.

Note~ Smell is only a temporary warning. Do not rely on your

nose.

200 ppm: your eyes and throat will begin to burn. and you will

get Headaches. Sense of smell lost rapidly.

300 ppm: Immediately Dangerous to Life and Health level.

Positive pressure breathing apparatus required.

500 ppm: Loss of reasoning and balance. Respiratory disturbances in 2 to 15 minutes.

700 ppm: Immediate unconsciousness. Death will result if not

rescued ASP.

1000 ppm: Immediate unconsciousness. Causes seizures, loss

of control of bowel and bladder. Breathing will stop and death

will result if not rescued promptly. Immediate resuscitation

needed.

Comparison of H2S with other lethal gasses will help you to

understand the importance why (a you can not work alone (b

the reason for prompt and swift action. H2S has a threshold limit of 20 ppm and a lethal concentration of 600 ppm.

Hydrogen cyanide (used in gas chambers) has a threshold

limit of 10 ppm and a lethal concentration of 300 ppm.

Carbon monoxide (CO) has a threshold limit of 50 ppm and a lethal concentration of 1,000 ppm.

You should by now be getting the picture and an

understanding of why so much preparation and precautions

need to be taken before any attempt is made to drill or

workover a well that expects to encounter H2s.

Over the following pages we will put together some useful

information that will show you that it can be drilled and drilled

safely providing you respect and follow the rules.

When using the term "the threshold limit". This is the

concentration at which it is believed you may be repeatedly

exposed, day after day, without adverse affects.

In many counters and state the ground rules are well defined

as to the approach that must be taken with providing the contingency plan for H2s. However it is the responsibility of

both Operator and contractor too provide such a plan and

training before an operation is permitted to commence

The purpose of the contingency plan is to provide an organized

plan of action for alerting and protecting the public prior to an

intentional release, or following the accidental release of a

potentially hazardous volume of hydrogen Sulphide.

Any operations subject to this H2s should develop and provide

an in-depth written contingency plan complete with all

requirements before hydrogen Sulphide operations are begun.

The conditions that might pose a threat in each area of

exposure must be considered when preparing the plan.

Such a plain should be graded in steps, dependent on condition that may prevail at the time of the release and taking into

account the worst circumstance an, "uncontrollable discharge or

pipe line fracture"

It must include instructions and procedures for alerting the

general public and public safety personnel of the existence of

an emergency, include procedures for requesting assistance

and for follow-up action to remove the public from an area of exposure.

Special instructions for conditions at a particular installation

such as local terrain and the effect of various weather

conditions must also be taken into account

The plan must be activated prior to an intentional release, or

immediately upon the detection of an accidental release of a potentially hazardous volume of hydrogen Sulphide include a

call list which shall include the following as they may be

applicable:

A well defined and structural chain of command must be

establish and in area of high risk rate drills that include all

member should be undertaken and if necessary include key

members of the public.

We would never consider working over a well or drilling a well

that contained high concentrations of hydrogen Sulphide gas

with untrained people. If working on land we must also

conceder the safety of the public this means educating them.

Supervisory personnel;

Offshore

This should include any shore base people such as the Rig

Superintendent on the drilling side and the Drilling

Superintendent on the operator side. They will continue and

follow up on their side. Alert the necessary department. Stand by boats, Supply boat. Fishing boat that may be in the area. Helicopters. Near by platforms. Gathering station. Any

operation within 3000 feet. Neighboring rigs.

Local Police:

They will inform the local community and if needed take the

necessary action and evacuate the area should the need arise.

Under such condition such people should be left alone to do

there work the plan must include a map detailing the area of

exposure. It should include the locations of private dwellings or residential areas, public facilities, such as schools, business

locations, public roads, or other similar areas where the public

might reasonably be expected within the area of exposure.

The plan must also include a list of the names and telephone

numbers of the responsible parties for each of the possibly

occupied public areas, such as schools, churches, businesses, or other public areas or facilities within the area of exposure.

Hospital

Ambulance service, Doctors, local clinic. area group such as the

St John Ambulance all need to be informed an involve and if

necessary train in emergency procedures

Contractors

For back up and supplemental equipment this should also

include the fire department.

Public Safety

The plan is to include names and telephone numbers of

residents within the area of exposure, and the provisions for

advance briefing of the public within an area of exposure. Such

advance briefing shall include the following subjects:

The necessity for an emergency action plan.

The possible sources of hydrogen Sulphide within the area of exposure;

Hazards and characteristics of hydrogen Sulphide.

Manner in which the public will be notified of an emergency.

Instructions on reporting a gas leak

Steps to be taken in case of an emergency.

Evacuation routes.

Location of safety and life support equipment;

Location of hydrogen Sulphide containing facilities

Location of nearby telephones and/or other means of

communication; and local radio station to tune into in an emergency.

Now day there is the web and a site should be set up to keep

the local people informed of any progress or potential

problems.

Transportation

Consideration must be given the transport in the area and

should involve Local or near by Airports, public transport and

the like

Emergency Procedures for H2S.

Hydrogen-Sulphide is one of the most vicious and deadly

hazards that can be encountered while drilling and forms

EXPLOSIVE mixtures with air. When drilling in an area where

hydrogen-Sulphide gas H2S might be encountered the rig

must be equipped to meet the and control even the smallest

shows.

Even in small amounts it is dangerous to your health. This is a

poisonous gas that can paralyze your breathing system and kill

within in minutes.

Equipment maintenance and supervision are priority with all

members of the crew being kept informed of the situation.

This is not the job of the rig crew and a service company should be engaged.

Constant training and drill should be organized with all

supporting elements. This should include any locale

community's. Contingence plans and safe areas must be well

established. With wind sock in full view.

"Never", never take a H2s operation lightly. Below you will find

an introduction but It is far from finished

General Notes

If a given concentration of H2S should occur on a drilling rig, it

is important that different procedures are made that must be

followed, depending on how dangerous a situation.

The personnel on the rig must know these procedures, which

must be regularly exercised; they must also be familiar with

the safety and emergency equipment to be used in such a

situation.

The following gives an example of how a plan containing safety and emergency procedures can be worked out for a off

shore operation

However this can be adapted to suite other types of operation.

By adding to or deducting from.

Although not hard and fast, it is a guide line for someone

having to prepare a rig. And was used to set up a Jack up rig

in 1989

The rig should be equipped with gas detectors, especially

designed for H2S, sensors should mounted at the rig floor,

shale shaker, cellar deck, mud pump room, control centre, air-

conditioning room. And mud logger shack

When encountering H2S, the primary or initial alarm in the

control centre "This could be the Tool pushers office" will tip at

20 ppm. The rig floor must be informed immediately.

(1) H2S conditions Pre-alarm

Crews should be notified from the drilling office and on the rig

"blackboard" several days in advance before reaching the

expected zone of H2S. All personnel should remain in a ready

condition to react at the sound of the gas alert.

Alarm Condition I

Gas concentration between 0 - 10 ppm.

No warning sign or alarm is used.

Control centre "could be Mud logging shack" should inform

driller and drilling office.

If equipment has not already been fitted personnel should

check safety and air breathing equipment for correct functioning and keep equipment available.

Operation Condition:-

Rig Floor Alarm Condition

Sufficient self-contained breathing apparatus sets should be kept on the rig floor for all personnel likely to be immediately

affected. The equipment will be rechecked at this stage.

Tests with a Draeger gas detector must be made immediately.

For this reason, a portable H2S detector must be available on the rig floor (driller house) at all times, with an adequate

supply of extra tubes.

The driller will notify the drilling superintendent, or tool-

pusher.

Check for gas with mud logging unit and start degasser.

Recheck your choke and kill manifold for correct line up.

Derrick man and shaker hand will be notified and instructed to

check and prepare breathing apparatus.

Have bug blower at shale shaker and pump room run at this

stage.

Have bug blower on top of draw works run.

Check "hang off" tools and safety valves and have everything

ready for circulating gas.

At least one P-tank with Barite will always be on pressure and

ready for use.

Personnel in connection with the mud system will wear breathing equipment at least 20 minutes prior to bottoms up.

Breathing apparatus will be worn at least 20 minutes, or 15

stands, in advance of core barrel on surface and retrieving

core.

Crane operator

Crane driver and safety man will check:

Safety Equipment

Breathing equipment for roustabouts and A.B.'s.

With Captain check "safe briefing area" and whether breathing

equipment and recharging equipment will have to be moved to

other "safe briefing areas".

With person in charge of breathing equipment and have

all equipment rechecked.

Crane driver will place bug blowers:

One at each entrance door to sack material stores, blower

facing in to sack stores.

One at starboard side of shale shaker building so that air can be blown into the shaker area from starboard.

Two at front end of cellar deck - facing towards aft end of

deck.

Crane driver will check with electrician re electrical connections

of bug blowers.

Crane driver will open both doors on port side of shaker house,

as well as all windows inside.

Crane driver and boatswain will close all watertight hatches in columns, namely:

Number 1 and 4 Starboard columns

Number 1 and 4 Port columns

Crane driver will check with rig floor for further instructions.

And will see that safety equipment will be taken to the "safe

briefing area".

Alarm Condition II

Gas concentration between 10 - 49 ppm. Moderate danger to

life.

The siren in the "drilling area" will sound automatically when

H2S concentration exceeds 15 ppm.

A close watch will be kept on the H2S detectors after the initial

alarm has tipped. When H2S is detected in quarters and/or

concentration of H2S gas reaches 20 ppm outside, anywhere

on the rig, the general "Gas Alert Signal" will be sounded.

All quarters will be evacuated and non-working personnel will

proceed to the "Gas Alert Stand-by Station" - "Safe Briefing

Station"

Drill crew and other essential personnel will commence to wear breathing apparatus and continue with their respective jobs -

bearing in mind that the "Buddy System" must be used while

wearing the breathing apparatus.

The Barge Captain will call the supply boat (stand-by boat)

and ask them to pick up his anchors and proceed to an upwind

position to await further instruction.

Radio communication shall be used to notify Shore Base and

helicopters at this stage.

Supervisors at the "Safe Briefing Area" will watch the

windsocks and flags to keep track if wind direction.

All personnel in contact with H2S will wear protective

breathing apparatus.

Alarm Condition II

Immediately the presence of Hydrogen-Sulphide at

concentration of 20 ppm is suspected, as indicated by the H2S

detector, all rig personnel will wear breathing apparatus.

Derrick man and shaker hand will be informed immediately

and instructed to wear their breathing apparatus.

Call drilling superintendent and Company representative.

Check H2S concentration with Draeger gas detector at:

Rig floor

Shale shaker

Mud pump room

Cellar deck

Start bug blower at standpipe manifold.

Keep contact with mud logging unit and engine control center

re H2S concentration.

Transfer Possum belly tank into active system and leave dump

valve open (overboard).

Open bottom valve (5") at poor boy degasser so that mud will be able to run from degasser into possum belly tank and

overboard. We will not circulate H2S gas-cut mud, but dump

all returns overboard.

All bug blowers at mud pump room, shaker area and cellar

deck to be started.

Alarm Condition II

Crane driver will

Close all watertight doors on deck.

Open all doors to cellar deck.

Set warning signs, reading "Danger - Poisonous Gas" at

forward and aft ladders to rig floor.

Crane driver will set warning sign, reading "Danger -

Poisonous Gas" at heliport facing so that the pilot will be able

to see the sign.

All non-essential personnel will proceed to the "safe briefing area".

Crane driver will stay in contact with drilling superintendent by

means of walkie-talkie Channel 13 for instructions

breathing equipment. As soon as this instruction is given, all essential personnel, i.e., all personnel outside the safe

Briefing area, will wear breathing apparatus.

Crane driver will start all bug blowers on main deck and at

shale shaker.

H2S Alarm Condition III

Gas concentration of 50 ppm or more is EXTREME DANGER TO

LIFE.

All non-essential personnel will prepare for evacuation.

Note: From the time Alarm Condition III is a fact, no

unauthorized personnel will be allowed to enter the shaker

area, cellar deck or mud pump room.

Notes and Information

The acceptable concentration for 8 hours exposure to H2S is

20 ppm. Hydrogen-Sulphide is heavier than air, colorless and

forms an explosive mixture with air between 4.3 and 46% by

volume. One breath of 1,000 ppm concentration

H2S will result in death within minutes.

The "Buddy System" Whenever H2S is suspected; personnel

must wear breathing apparatus before entering the

contaminated area and MUST have a "back-up man" (buddy),

also with breathing apparatus, available.

Safe Briefing Stations the Barge Captain will indicate these on

the rig "black-board".

There will be two briefing stations so that one is always

upwind of the drilling rig. Spare air bottles will be stored at the

"safe briefing area" and bottles must only be changed at this

point.

The "NO SMOKING RULES" will be followed outside all living

quarters as soon as "Alarm Condition 1" has been put into

force.

As the above introduction stated, we are drilling in a very

dangerous area with a very dangerous gas. As every man on

the rig at all times will have to be ready for H2S, and must be

trained accordingly.

The rig has to be equipped with sufficient breathing equipment

for all personnel onboard. This should include the maximum of

service people that could be at the rig at any one time.

As the accurate function of the facemask depends on how

airtight the mask seals to your face, you will be asked to

remove your beard (facial hair) or assume responsibility for

risk of death or serious bodily harm.

Alarm Condition

Killing the well with weighted mud, dumping gas cut mud

through poor boy degasser and possum belly.

All rig personnel will wear breathing apparatus.

Non-essential personnel will leave the rig floor for "safe

briefing area".

Crane driver will

Lay down crane not required.

Pick up walkie-talkies and distribute to rig floor and Barge

Captain and Tool pusher. All radios to be on stand-by Channel

13.

Assist boatswain with anchor winches.

Check personnel basket on upwind side. Stay in contact with

rig floor for possible extra personnel.

Barge Engineer will

Set all anchor winches and clutches in gear and check for

sufficient power to winch.

Place a walkie-talkie Channel 13 at each anchor winch control house.

Check with portable gas detector that upwind crane deck is

free of H2S.

In case of evacuation, boatswain will assist crane driver at upwind crane.

Notes and Information

The acceptable concentration for 8 hours exposure to H2S is 20 ppm. Hydrogen-Sulphide is heavier than air, colourless

and forms an explosive mixture with air between 4.3 and 46%

by volume. One breath of 1,000 ppm concentration

H2S will result in death within minutes.

The "Buddy System"

Whenever H2S is suspected, personnel must wear breathing

apparatus before entering the contaminated area and

MUST have a "back-up man" (buddy), also with breathing

apparatus, available.

Safe Briefing Stations the Barge Captain will indicate these on

the rig "black-board". There will be two briefing stations so

that one is always upwind of the drilling rig. Spare air bottles

will be stored at the "safe briefing area" and bottles will only

be changed at this point.

The "NO SMOKING RULES" will be followed outside all living

quarters as soon as "Alarm Condition 1" has been put into

force.

As the above introduction stated, we are drilling in a very

dangerous area with a very dangerous gas. As every man on

the rig at all times will have to be ready for H2S, you will be

trained accordingly.

The rig is equipped with sufficient breathing equipment for all

personnel onboard. As the accurate function of the facemask

depends on how airtight the mask seals to your face, you will

be asked to remove your beard (facial hair) or assume

responsibility for risk of death or serious bodily harm.

One deep breath of highly concentrated H2S will cause death. Therefore, when depending upon an air pressure mask to

breathe, vision becomes a major factor. Facial hair may reduce

visibility.

One person will be responsible for the upkeep of all breathing

equipment.

All watertight bulkhead doors and hatches must be kept closed at all times from the moment the general gas alarm has

sounded.

Safety Equipment

Portable Gas Detecting Instruments.

Rig Floor

Drilling Office

Control Center

Frequent inspections of all areas of poor ventilation should (and will) be made with portable gas detecting instruments. (See above).

Prior to the "All Clear Signal", quarters and all other areas will

be checked with portable H2S detectors.

Eyewash Stations

Crane deck on both sides, at bulk-loading manifold.

Bridge.

Accommodation.

Radio station, toilet.

Stretcher

Hospital

Locker outside Hospital

First Aid Kit - at the Hospital

Safety Belts - to be placed at the Safe Briefing Areas and Heliport Fire Fighting Station.

Bug Blowers There will be bug blowers available to circulate

possible H2S gas out of closed areas such as: Pump room

Shale shaker Cellar deck Rig floor Bug blowers will be placed

at the sack stores doors and starboard entrance to the shale

shaker area, as well as the front Cellar deck.

Resuscitator (folding bag)

Drilling office Hospital

H2s The Rescue

Use safe work practices to avoid exposure. and remember (prevention is better than cure.)

The Buddy System

The buddy system is the best way to ensure that a rescue is

started immediately. There is no time for delay, and the

response must be immediate if a team member is overcome. When a buddy is in trouble, their buddy should know, and

initiate the seven step initial response strategy as taught in

every H2S schools.

Safe areas and Head counts are only back-up systems to the

buddy system. The buddy system is the backbone and the

quick response team

The safety of the rescue team is a prime consideration.

The rescue must not be carried out unless the rescuers are

protected by breathing apparatus and without taking into

account the fire hazard associated with a gas leak.

The rescue team should also consider delaying such an

operation if a sources of ignition is immediately downwind of

the leak.

Where possible remove the victim from the gas first then stop

the leak and allow the gas to blow away, or if it is possible do

both. Do not move the victim into a safe area unless you are

absolutely sure that the gas will not reach the area where first

aid is being done.

If in doubt, move farther out (upwind from the source of the gas.)

If breathing has stopped, some form of artificial respiration is

needed. The sooner this is in force the better and the more

likely the victim is to survive without permanent damage.

Mouth to mouth artificial respiration is, suggested to be the

best treatment for a non breathing victim of H2S. There are

three big advantages to mouth to mouth:

1. No chance for mistakes - if you are doing it correctly. You

can feel the air go in and feel it come back out against your cheeks.

2. Faster recovery - H2S interferes with the way that nerve

cells use oxygen to produce signals. When the nerves of the

respiratory system are not sending sufficient signals, breathing

stops. The extra carbon dioxide in our breath when we are doing mouth to mouth seems to stimulate the remaining nerve

cells so that spontaneous breathing returns more quickly.

3. A rescuer doing mouth to mouth will be aware of the return

of breathing and can place the victim in the recovery position.

Some victims experience nausea and vomiting after exposure to H2S. This will not occur until consciousness returns.

Consciousness normally doesn't return until after spontaneous

breathing returns.

The victims will be confused and frightened when they regains

consciousness and the face to face position allows the best

communication. This position also allows the victim to be

turned easily at the first sign of vomiting therefore the position

the rescuer takes while doing mouth to mouth (kneeling

beside the victims head) is also has advantages. There have been reports of convulsions being a symptom of H2S poisoning and the rescuer can easily avoid being struck.

Keeping your cool, rescue and resuscitation should be done

calmly, quietly and gently, after the victim is breathing

normally, allow them rest quietly. Keep them warm by using a

using a blanket this will help to reduce shock. Talk to them,

give them reassurance, let them know the emergency is over

and it is once breathing has been restored.

Once a victim has recovered sufficiently and they are sitting up

and talk normally, any other symptoms of the acid gas effects

of H2S exposure can be treated. Eyewash and dark glasses for the sore eyes, a soothing drink such as water or milk for the

sore throat.

Part of any recovery is the feel good scenario, so when a

victim feels up to it they should change their clothes, wash up,

gather up their belongings, then they should be taken to medical aid.

People that have been involved and lost consciousness from

H2S exposure must be seen by a doctor because of the chance

of pulmonary edema (Swelling from excessive accumulation of

serous fluid in tissue).

Do not allow them to make their one way or drive themselves

as their coordination has probably been affected. They must

not return to work, not only because of their coordination but

also because there is the possibility of severe permanent

effects on people that are gassed twice in the same day.