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== Air Sampling for Naphtha’s Air sampling is conducted to identify and evaluate employee or source exposures of potentially hazardous gas, vapor or particulates; assess compliance; and evaluate process or reformulation changes.

Active and passive air sampling methods for naphtha vapors are covered in this process review. Direct reading instruments and dusts and particulates are not discussed in this review.

I Properties of Naphtha’s

Health Hazards

“Light naphtha, a mixture consisting mainly of straight-chained and cyclic aliphatic hydrocarbons having from five to nine carbon atoms per molecule. Heavy naphtha, a mixture consisting mainly of straight-chained and cyclic aliphatic hydrocarbons having from seven to nine carbons per molecule.”  “Almost all volatile, lipid-soluble organic chemicals cause general, nonspecific depression of the central nervous system or general anesthesia.”  The OSHA PEL TWA = 100 parts-per-million (ppm); Health Hazards/Target Organs = eyes, skin, RS, CNS, liver kidney. Symptoms of acute exposure are dizziness and narcosis with loss of consciousness. The World Health Organization categorizes health effects into three groups: reversible symptoms (Type 1), mild chronic encephalopathy (Type 2) and severe chronic toxic encephalopathy (Type 3).

Physical Properties

Molecular weight is 100-215; specific gravity is 0.75- 0.85; boiling point is 320-430 F; vapor pressure is < 5 mm HG. Naphtha’s are insoluble in water; colorless (kerosene odor) or red-brown (aromatic odor) liquid; incompatible with strong oxidizers.

II Air Sampling Categories: Direct Reading versus Sample Collection

Two categories of air sampling equipment exist, they are: direct reading and sample collection. Direct reading equipment provides immediate measurement of exposure concentration. Sample collection includes samples of air collected over a period of time and weighed and analyzed in the laboratory. Sample collection involves active and passive air monitoring methods. Air sampling instruments will be discussed during this air sampling process review; Direct reading air monitor instruments and methods will not be discussed at this time.

III Sampling Methods: Active versus Passive Sampling

Active Sampling

Active sampling relies on sampling pumps to draw air and chemicals vapors or gases to adsorbent filter materials.

Passive Sampling

Passive monitors rely on collection of gases and vapors through passive diffusion (Ficks Law) to allow personal sampling without use of pumps. Diffusion is the movement or passage of chemical molecules through a semi-permeable barrier from the source of higher concentration gradient to a lower concentration.

IV Sampling Types: Personal, Area, Grab and Integrated Sampling

Personal Sampling

Personal sampling is used to evaluate employee exposure to naphtha. The employee wears the sampling device that collects an air sample representative of air exposure for a specific period of time. The quantity of chemical sampled is collected on the sorbent or filter and then calculated against the total volume employee air exposure.

Area Sampling

Area Sampling is used to evaluate background exposure to leaks and implement control measures.

Grab Sampling

Grab sampling is used to monitor extremely toxic environments over a short period of time or to determine if additional air monitoring is required for over-exposure. Integrated Sampling

Integrated exposure sampling is used to determine the 8-hour time weighted average exposure because various exposure concentrations are integrated during the sampling period.

V Absorption versus Adsorption

Absorption

Gas or vapor is removed from the air stream as it passes through the absorption liquid used in impingers (gas washing bottles), fritted bubblers and midget impingers. Collection liquid can be reactive or non-reactive. Gas or vapor is separated and analyzed under laboratory conditions.

Adsorption “Air sampling for insoluble or non-reactive gaseous substances is commonly conducted with tubes filled with granular sorbent such as charcoal (non- polar properties) and silica gel (polar properties).”  Activated charcoal is used primarily for organic vapors and has a surface area > 1000 m2/g. Charcoal tubes are composed of coconut shell or petroleum based charcoal. Tubes vary in length and width. First section contains 100 mg of charcoal and the second section contains a number of mg of charcoal. The second section contains generally one-half the volume of the first. Breakthrough is where > 10% of mass in front section breaks through to second section and indicates that the contaminant may not have been collected properly and invalidates the results.

VI Breathing Zone Air Sampling Procedures

Sampling Train

Active air sampling devices consist of five sections starting at the suction pump: •	“Air inlet orifice is the opening where air enters the inlet. •	Collection devices retains chemical on the collection media as air and chemical mixture travel through collection device. •	Flow rate control valve controls the flow rate traveling through the meter. •	Air flow meter records the air flow rate traveling through the meter. •	Suction pump moves air through the collection device.”

Break both ends of sorbent tube using sorbent tube breaker. Insert sorbent tube into the rubber sleeve of the adjustable low flow holder or tube holder. The arrow on the sorbent tube indicates air flow towards the pump. In the absence of an arrow insert the end of the tube with the smallest sorbent section into the tube holder. Connect the loose end of the flexible tubing into the pump inlet

VII Active Air Sampling Method for Naphtha’s – 34 Steps

Preparation & Calibration

1	Prepare and calibrate the sampling equipment by charging batteries of the active sampler. 2	Verify that sufficient varieties and quantities of detector tubes are available for air sampling. 3	Determine the sampling technique (NIOSH, OSHA). 4	Follow published air procedure/method NIOSH 1550 or OSHA 1500 for naphtha related solvents. 5	Calibrate the sampler pump, sampling device, sorbent tube and with a standard rotameter. 6	Set air pump sampling rate at .01 L and .2 L/min for OSHA or NIOSH. 7	Record the pump rotameter reading. 8	Calibrate pump rate specified in the method.

Communication

9	Select the employees to be monitored. 10	Discuss the sampling purpose and process with the employee. 11	Let the employee know the sampling period length. 12	Instruct the employee not to tamper with air monitoring equipment. 13	Employee should notify Industrial Hygienist if they have question about equipment or equipment needs to be removed. 14	Employee should document unusual production or exposure events during the course of monitoring.

Adsorbent Tube Orientation

15	Attach the air pump on the employee’s belt. 16	The sorbent tube with more charcoal should be facing away from the pump. Place the inlet in a downward vertical position to avoid contamination 17	Break open the ends of the filter or charcoal tube (with tube breaker and safety glasses) before sampling begins. 18	Attach the collection device (charcoal tube or passive sampler) to the shirt collar or as close as possible to the breathing zone (in a 12 inch sphere from around the head). 19	Attach the sorbent tube holder clip on the protective cover near the breathing zone. 20	 Place and secure (duct tape) the monitoring equipment on the employee so it does not interfere with the employees work (excess tubing should be taped out of the way as well). 21	“Record location of sample, employee name and identification number, title, chemicals sampled for, starting/ending times, flow rate starting/ending flow rates, temperature, humidity, barometric pressure, active/passive sampling, sampling media, job activity.”

Active Air Sampler Rate Verification

22	Turn the air pump on and document the time start. 23	Record the data by sampling protocol, sampling integrity. 24	Check the air monitoring pump, hose, rate and filtering devices during the air monitoring event. Record pump rotameter reading. 25	Sample at the target sample rate. 26	Take digital pictures, document conditions, emission sources, work practices, activities. 27	Prepare blanks during the sample period (Minimum 20 % of samples). Field blanks should be subjected to same handling as the samples except that no air is drawn through them. 28	Prior to pump removal verify pump rate with rotameter within the local sampling atmosphere location to account for humidity and temperature. 29	Record pump rotameter reading 30	“Turn off pump and record ending time.” 31	Remove the sorbent tube, seal the ends and document any pertinent sampling information. 32	Prepare the chain of custody and the samples for delivery to the lab for analysis 33	Pack samples for shipment (Different methods may require preservative for shipment). 34	Ship samples to AIHA accredited lab.

VIII Secondary Calibration Rotameter

Rotameter consists of a float ball moving vertically in a tapered tube. Force of air flow volume pumped through the air tube counteracts gravity. Air sampling pump is calibrated against the soap bubble meter attached to sampling train. Calibration will represent the current sampling air temperatures and pressures accurate to plus or minus 5 %.

IX Minimum Sampling Volumes

Determine the minimum sampling volume required for analysis by calculating the Limit of Detection of the analytical method. Determine how much air sample must be drawn through the sample collector for sufficient capacity of analysis, prevent chemical interference and not exceed sampler capacity.

Limit of Detection Formula for Analytical Method and Example:

Example Problem: The limit of detection for an analytical method is .01 mg. It is desired to be able to detect 0.02 mg/M3. How much air must be drawn through the sample collector? Formula TC = LOD  / LOQ

Definitions TC			= Target Concentration LOD       	= Limit of Detection for Analytical Method - OSHA 1500 & NIOSH 1550 LOQ        	= Exposure Limit of Quantification in Mg/M3

OSHA/ NIOSH Naphtha Method: Given Values for Example LOD 		 	= 0.01 mg 1000 L 			= 1 M3 LOQ			= 0.2 mg/M3

Calculations .01 mg/M3 x 1000L /.2 L/min = 50 Liters X Complications with Air Sampling

Air sampling complications can be interference with chemicals (alcohols, ketones, ethers, and halogenated hydrocarbons), vapors, sampling media, humidity, temperature, barometric pressure, atmospheric dust, water vapor and container.

XI Adsorbent Tube Advantages and Disadvantages

Break through occurs from the following: sampling too fast; chemical adsorption migration greater than 10% into the second stage of the sorbent tube; and/or sampling at high analyte levels. Sorbent tubes are usually accurate to plus or minus 25% at the PEL. “Air sampling devices have unique capacities for each analyte sampled. When this capacity is exceeded; analyte breakthrough occurs. An analyte of interest can be can be displaced by an analyte more strongly adsorbed by the adsorbent.”

“High humidity can severely reduce the breakthrough volumes of adsorbents like charcoal and silica gel.”

XII Sorbent Tube Desorption

Naphtha’s sorbent tube is desorbed of collected chemical by carbon disulfide for 30 minutes. XIII Advantages and Disadvantages of Passive Sampling

Passive monitoring (badge or tube) is cheaper and easier for occupational hygienist to use and require less technical training. Diffusion sampling is less cumbersome for the wearer. Passive sampling is not impacted by pressure and temperature variations like active sampling.

Passive sampling disadvantages are that some chemicals are not easily retained on to diffusion sorbent. Stagnant and high face velocities do not allow for accurate diffusion onto passive diffusion samplers.

XIV Analyzing Method

Naphtha’s analysis method is gas chromatography – flame ionization detector (GC – FID).

Results versus Standards

Any sample result that is less than the OEL is usually considered to be in compliance with the law at the 95% confidence level. Exposures over the PEL and LCL may result in citations and fines. If the PEL for a chemical is 50 ppm and an employee had a TWA of 60 ppm for a 6-hour shift. This may look like an overexposure however upon recalculation for a full work shift (8-hours) the TWA comes out to be: Chemical exposures may result in frequent or higher excursions during the work shift and may or may not meet the regulatory guidelines. Pregnant women, the very young and very old are more susceptible to chemical exposures. Preferred controls remove or drastically reduce the overall exposure to an acceptable exposure level.

The Industrial Hygiene Code of Ethics requires placing employee health first in all considerations. If the PEL’s are not available, animal studies or toxicology data may provide guidance.

Limitations or disadvantages of United States PEL’s are the following: PEL’s are limited only to inhalation exposures, PEL’s apply to health guidelines established in 1989, PEL’s do not consider chronic toxicity data or sensitizers or skin notations, PEL’s considers a health exposure risk of 1:1000 risk for cancer versus environmental risks of 1:1,000,000, PEL’s fail to account for multiple exposures, and PEL’s are listed on only 10% of the chemicals used in the work place.

The minimum standard of care in many industries is the maintenance of airborne chemical concentrations below all existing standards, guidelines and internally generated standards. XV Air Sampling PPE

Industrial hygienist (IH) conducting air sampling are required to wear all Federal, State and Local, customer, industry specific and company required (PPE) personal protective equipment but not limited to: steel toe boots, work trousers, work shirt, (nomex coveralls if required), nitrile gloves, hard hat minimum Type C, safety glasses, etc.

XVI Health Assessment, Interviews and Evaluation

Conduct opening conference to discuss the reasons that you are there: Assist management in proactive evaluation of current health conditions; control of any current or potential health issues and anticipate potential safety and health considerations.

Review historical conditions by reviewing OSHA 300 log and historical/current health surveillance programs. Surveillance programs should contain biological monitoring for biomarkers (biological markers of blood or urine) or metabolites (by-products) of exposure to various chemicals. “ACGIH, biological monitoring should be complimentary to air monitoring.”

Evaluate current conditions by photographing, videotaping and documenting work processes where potential health problems may occur. Security clearances and work site guide are recommended prior to tours and evaluation. Proprietary, health exposure and ignition considerations should be addressed prior to walk-through.

Employee health complaints, symptoms, odors, interviews, etc.; all lead to an air monitoring strategies. Air sampling processes follow with sample analysis and comparison against health standards lead to employee/management exposure communications.

Exposure information allows management to understand work place health exposures and then implement health prevention strategies to control and prevent chemical exposures. Health exposure assessment, communications, awareness, training, engineering, administrative and personal protective strategies address reduction and elimination of potential or real naphtha exposures. Individual historical and community health considerations are also taken into account. XVII Toxicity

Toxicity dose response exposures may be impacted (either decreased or increased) by the following factors. Chemical factors impact toxicity such as: concentration or quantity (harm in dose) times duration, hormesis (low dose stimulation), additivity, competition, synergism, antagonism, dispersability, water solubility, heavier or lighter than air, media exposure (liquid, gas, vapor, aerosol), molecule or particle size, toxicity of dose, toxicodynamics (what the chemical does to the body), progressive, permanent and reversible effects, bioavailability (binding or interference with the chemical), persistence, psychological impact, metals in different oxidative state, mechanism of action, sub cellular level, nanotechnology, receptors, and free radicals.

Individual biological factors such as stress, respiratory rate, gender, age, race, sweating, individual susceptibility, route of entry (injection, dermal, ingestion, inhalation, ocular), perfusion, affinity (binding, lipophilicity, storage) toxicokinetics (what body does to chemical), rate of uptake, detoxification excretion, elimination, transport, metabolism or biotransformation, water solubility, absorption, digestion or adsorption, systemic impact or local impact on body systems. Environmental factors impact chemical and particulate exposures such as: heat, cold, precipitation, inversions versus clear days and air pressure.

XVIII Exposure Control

Primary health prevention methods focus on chemical exposures prior to occurrence. Engineering prevention controls would be substitution, automation, enclosure, elimination, isolation and change of process. Ventilation controls would be local exhaust ventilation and vacuum operations. Administrative prevention controls would be work practice change, education, training, job rotation, job reduction, work schedules, substitution, job reassignment, wet work methods, maintenance and housekeeping. Secondary health prevention methods focus on early identification and treatment of           chemical exposures for cure and treatment. Personal protective equipment could be air-purifying cartridge and powered air-purifying cartridge and supplied (air hose, self contained or re-breather) respirators; gloves (PVA, viton, neoprene). Tertiary health prevention methods are treatment and rehabilitation of employees exposed to chemical overexposure in the work place. End ==